Network Working Group                                              X. Wu
 Internet-Draft                                            H. Schulzrinne
 Expires: August 18, 2005                             Columbia University
                                                        February 14, 2005


     LESS: Language for End System Services in Internet Telephony
                          draft-wu-iptel-less-00

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 Copyright Notice

    Copyright (C) The Internet Society (2005).

 Abstract

    In Internet telephony, end systems can take a large role in providing
    services, especially in networks without pre-configured
    infra-structure, such as peer-to-peer networks.  Since we believe
    that end system services differ in their requirements from network
    services, we define a new service creation scripting language called
    the Language for End System Services (LESS).  LESS inherits many



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    characteristics from the Call Processing Language (CPL).  It contains
    commands and events for direct user interaction and the control of
    media applications.  This document defines the basic elements of LESS
    and several commonly used LESS extensions.

 Table of Contents

    1          Introduction ........................................    7
    1.1        Conventions of This Document ........................    7
    2          LESS design decisions ...............................    8
    2.1        High-level Structure ................................    8
    2.2        Simplicity ..........................................    9
    2.2.1      Familiarity .........................................    9
    2.2.2      Generality ..........................................   10
    2.2.3      Uniformity ..........................................   10
    2.2.4      Analyzability .......................................   11
    2.3        Safety ..............................................   11
    2.3.1      Type safety .........................................   11
    2.3.2      Control flow safety .................................   12
    2.3.3      Memory access .......................................   12
    2.3.4      LESS engine safety ..................................   13
    2.3.5      Using third-party created or auto-generated
               service scripts .....................................   13
    3          LESS elements .......................................   13
    4          Variables ...........................................   15
    4.1        System information ..................................   15
    4.2        User information ....................................   15
    4.3        Agent information ...................................   15
    4.4        Trigger information .................................   16
    4.5        Action information ..................................   16
    5          Basic LESS elements .................................   16
    5.1        Triggers ............................................   16
    5.1.1      "incoming" trigger ..................................   16
    5.1.2      "timer" trigger .....................................   16
    5.2        Switches ............................................   17
    5.2.1      "time-switch" .......................................   17
    5.2.2      "address-switch" ....................................   17
    5.2.3      "priority-switch" ...................................   17
    5.2.4      "string-switch" .....................................   17
    5.2.5      "language-switch" ...................................   18
    5.2.6      "status-switch" .....................................   18
    5.3        Modifiers ...........................................   19
    5.3.1      "location" Modifier .................................   19
    5.3.2      Location Lookup .....................................   19
    5.3.3      Location Removal ....................................   19
    5.4        Actions .............................................   19
    5.4.1      "accept" ............................................   19
    5.4.2      "reject" ............................................   20



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    5.4.3      "redirect" ..........................................   20
    5.4.4      "authenticate" ......................................   20
    5.4.5      "call" ..............................................   21
    5.4.6      "terminate" .........................................   21
    5.4.7      "mail" ..............................................   22
    5.4.8      "log" ...............................................   22
    5.4.9      "wait" ..............................................   23
    6          Subactions and Ancillary Information ................   23
    7          Security Considerations .............................   23
    8          IANA Considerations .................................   23
    8.1        URN Sub-Namespace Registration for
               urn:ietf:params:xml:ns:less .........................   24
    8.2        Schema registration .................................   24
    8.3        MIME Registration ...................................   24
    9          LESS Extensions .....................................   25
    10         Media handling extension ............................   26
    10.1       Modifiers ...........................................   26
    10.1.1     "Media:media" Modifier ..............................   26
    10.2       Actions .............................................   27
    10.2.1     "Media:mediaupdate" Action ..........................   27
    10.3       IANA Considerations .................................   27
    10.3.1     URN Sub-Namespace Registration for
               urn:ietf:params:xml:ns:less:media ...................   28
    10.3.2     Schema registration .................................   28
    10.3.3     MIME Registration ...................................   28
    11         Mid-call Handling extension .........................   29
    11.1       Actions .............................................   29
    11.1.1     "Midcall:transfer" Action ...........................   29
    11.1.2     "Midcall:merge" Action ..............................   30
    11.2       IANA Considerations .................................   30
    11.2.1     URN Sub-Namespace Registration for
               urn:ietf:params:xml:ns:less:midcall .................   30
    11.2.2     Schema registration .................................   31
    11.2.3     MIME Registration ...................................   31
    12         User Interaction extension ..........................   31
    12.1       Triggers ............................................   31
    12.1.1     "UI:command" Trigger ................................   31
    12.2       Actions .............................................   32
    12.2.1     "UI:alert" Action ...................................   32
    12.2.2     "UI:getinput" Action ................................   33
    12.3       IANA Considerations .................................   33
    12.3.1     URN Sub-Namespace Registration for
               urn:ietf:params:xml:ns:less:ui ......................   33
    12.3.2     Schema registration .................................   34
    12.3.3     MIME Registration ...................................   34
    13         Instant Messaging extension .........................   34
    13.1       Triggers ............................................   34
    13.1.1     "IM:message" Trigger ................................   34



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    13.2       Actions .............................................   35
    13.2.1     "IM:sendmsg" Action .................................   35
    13.3       IANA Considerations .................................   35
    13.3.1     URN Sub-Namespace Registration for
               urn:ietf:params:xml:ns:less:im ......................   36
    13.3.2     Schema registration .................................   36
    13.3.3     MIME Registration ...................................   37
    14         Event Handling extension ............................   37
    14.1       Triggers ............................................   37
    14.1.1     "Event:subscription" Trigger ........................   37
    14.1.2     "Event:notification" Trigger ........................   37
    14.2       Switches ............................................   37
    14.2.1     "Event:event-switch" Switch .........................   37
    14.3       Actions .............................................   38
    14.3.1     "Event:approve" Action ..............................   38
    14.3.2     "Event:deny" Action .................................   38
    14.3.3     "Event:defer" Action ................................   39
    14.3.4     "Event:subscribe" Action ............................   39
    14.3.5     "Event:notify" Action ...............................   40
    14.4       IANA Considerations .................................   41
    14.4.1     URN Sub-Namespace Registration for
               urn:ietf:params:xml:ns:less:event ...................   41
    14.4.2     Schema registration .................................   42
    14.4.3     MIME Registration ...................................   42
    15         Location-based service extension ....................   42
    15.1       Switches ............................................   42
    15.1.1     "Location:where-switch" Switch ......................   43
    15.1.2     "Location:where-relation-switch" ....................   45
    15.2       IANA Considerations .................................   47
    15.2.1     URN Sub-Namespace Registration for
               urn:ietf:params:xml:ns:less:location ................   47
    15.2.2     Schema registration .................................   47
    15.2.3     MIME Registration ...................................   48
    16         Queue handling extension ............................   48
    16.1       Actions .............................................   48
    16.1.1     "Queue:enqueue" Action ..............................   48
    16.1.2     "Queue:dequeue" Action ..............................   48
    17         Examples ............................................   49
    17.1       Q.1211 services .....................................   49
    17.1.1     Abbreviated dialing (ABD) ...........................   49
    17.1.2     Attendant (ATT) .....................................   50
    17.1.3     Authentication (AUTC) ...............................   50
    17.1.4     Authorization code (AUTZ) ...........................   51
    17.1.5     Automatic call back (ACB) ...........................   51
    17.1.6     Call distribution (CD) ..............................   52
    17.1.7     Call forwarding (CF) ................................   52
    17.1.8     Call forwarding on busy/don't answer (CFC) ..........   52
    17.1.9     Call gapping (GAP) ..................................   53



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    17.1.10    Call hold with announcement (CHA) ...................   53
    17.1.11    Call limiter (LIM) ..................................   54
    17.1.12    Call logging (LOG) ..................................   55
    17.1.13    Call queueing (QUE) .................................   55
    17.1.14    Call transfer (TRA) .................................   56
    17.1.15    Call waiting (CW) ...................................   56
    17.1.16    Closed user group (CUG) .............................   57
    17.1.17    Consultation calling (COC) ..........................   57
    17.1.18    Customer profile management (CPM) ...................   57
    17.1.19    Customer recorded announcement (CRA) ................   57
    17.1.20    Customized ringing (CRG) ............................   58
    17.1.21    Destination user prompter (DUP) .....................   59
    17.1.22    Follow-me diversion (FMD) ...........................   59
    17.1.23    Mass calling (MAS) ..................................   59
    17.1.24    Meet-me conference (MMC) ............................   59
    17.1.25    Multi-way calling (MWC) .............................   60
    17.1.26    Off-net access (OFA) ................................   60
    17.1.27    Off-net calling (ONC) ...............................   60
    17.1.28    One number (ONE) ....................................   61
    17.1.29    Origin dependent routing (ODR) ......................   61
    17.1.30    Originating call screening (OCS) ....................   62
    17.1.31    Originating user prompter (OUP) .....................   62
    17.1.32    Personal numbering (PN) .............................   62
    17.1.33    Premium charging (PRMC) .............................   62
    17.1.34    Private numbering plan (PNP) ........................   63
    17.1.35    Reverse charging (REVC) .............................   63
    17.1.36    Split charging (SPLC) ...............................   63
    17.1.37    Terminating call screening (TCS) ....................   63
    17.1.38    Time dependent routing (TDR) ........................   64
    17.2       5ESS services .......................................   64
    17.2.1     Attendant call transfer (also known as Call
               splitting) ..........................................   64
    17.2.2     Attendant camp-on ...................................   65
    17.2.3     Attendant conference ................................   66
    17.2.4     Authorization code ..................................   67
    17.2.5     Automatic recall ....................................   67
    17.2.6     Call forwarding busy line (CFBL) ....................   68
    17.2.7     Call forwarding busy line--incoming only ............   69
    17.2.8     Call forwarding--don't answer .......................   69
    17.2.9     Unconditional call forwarding .......................   70
    17.2.10    Call hold ...........................................   70
    17.2.11    Call transfer--individual--all calls ................   70
    17.2.12    Call waiting and cancel call waiting ................   71
    17.2.13    Circle hunting ......................................   72
    17.2.14    Conference calling ..................................   72
    17.2.15    Customer-changeable speed calling ...................   72
    17.2.16    Direct connect ......................................   73
    17.2.17    Distinctive ringing .................................   73



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    17.2.18    Four- and eight-party ...............................   74
    17.2.19    Recorded telephone dictation ........................   74
    17.2.20    Time-of-Day features ................................   75
    17.2.21    Message services ....................................   75
    17.2.22    Multibutton key telephone system (MBKS) .............   76
    17.2.23    Group alerting ......................................   76
    17.3       Services defined in CSTA Phase III ..................   77
    17.3.1     Accept call .........................................   78
    17.3.2     Alternate call ......................................   78
    17.3.3     Answer call .........................................   78
    17.3.4     Call back call-related ..............................   78
    17.3.5     Call back message call-related ......................   78
    17.3.6     Camp on call ........................................   79
    17.3.7     Clear call ..........................................   79
    17.3.8     Clear connection ....................................   79
    17.3.9     Conference call .....................................   80
    17.3.10    Consultation call ...................................   80
    17.3.11    Deflect call ........................................   80
    17.3.12    Dial digits .........................................   80
    17.3.13    Directed pickup call ................................   80
    17.3.14    Group pickup call ...................................   80
    17.3.15    Hold call ...........................................   80
    17.3.16    Intrude call ........................................   81
    17.3.17    Join call ...........................................   81
    17.3.18    Make call ...........................................   81
    17.3.19    Make predictive call ................................   81
    17.3.20    Park call ...........................................   82
    17.3.21    Reconnect call ......................................   82
    17.3.22    Retrieve call .......................................   82
    17.3.23    Send message ........................................   82
    17.3.24    Single step conference call .........................   82
    17.3.25    Single step transfer call ...........................   82
    17.3.26    Transfer call .......................................   83
    17.4       New services ........................................   83
    17.4.1     Email ...............................................   83
    17.4.2     Web .................................................   83
    17.4.3     Instant messaging ...................................   84
    17.4.4     Event subscription and notification .................   84
    17.4.5     Event notification and event-based services .........   85
    17.4.6     Location-based services .............................   85
    18         Feature Interaction Handling Algorithm for LESS
               Scripts .............................................   86
    18.1       Tree merging algorithm ..............................   86
    19         The XML Schema for LESS and Commonly Used
               Extensions ..........................................   89
    19.1       XML Schema for LESS .................................   89
    19.2       XML Schema for LESS Media Extension .................  104
    19.3       XML Schema for LESS Mid-call handling Extension .....  119



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    19.4       XML Schema for LESS User Interaction Extension ......  121
    19.5       XML Schema for LESS Instant Messaging Extension .....  123
    19.6       XML Schema for LESS Event Handling Extension ........  124
    19.7       XML Schema for LESS Location-based Services
               Extension ...........................................  128
    19.8       XML Schema for LESS Queue Handling Extension ........  134
    20         References ..........................................  136
    20.1       Normative References ................................  136
    20.2       Informative References ..............................  137
             Authors' Addresses ....................................  137
             Intellectual Property and Copyright Statements ........  139








































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 1 Introduction

    One of the key promises of Internet telephony lies in the ability of
    developing and deploying innovative services rapidly and efficiently.
    Internet telephony services are not limited to those performed in
    servers operated by service providers; end systems can play a much
    larger role in providing services than in traditional telephone
    networks.

    We define end systems as the systems that are located at the end of a
    session signaling routing path and can initiate or accept session
    setup messages. By this definition, end systems are not limited to
    the user-operated systems, instead, they can also be conference
    servers.  Accordingly, we define network servers as the entities that
    perform session message routing. We believe it is necessary to define
    a service creation language specifically for end systems because end
    system services are different from network services.

    There are services that are clearly implementable only in end systems
    or in network, but most can be moved to either location, or split
    between the two.  Providing services in user-operated end systems has
    the advantage that on-the-spot interaction with users is much easier.
    Network services can only interact via protocol messages and possibly
    media content, rather than GUIs. It might be possible to incorporate
    user interaction into scripts running in servers, but it is likely to
    be far more cumbersome and subject to network delays.

    In Internet telephony, usually end systems are the only entities
    where signaling and media flows converge. This is different from the
    legacy PSTN. Thus, any service that requires interaction with user
    media is likely to be easier to implement in end systems. The more
    detailed analysis on the differences between end system services and
    network services can be found in our articles [11] [12].

    Because of the differences between end system services and network
    services, we define the Language for End System Services specifically
    for end system service creation. Section 2 introduces the design
    decisions for LESS. Section 3 briefly describe the categories of
    elements in LESS, we then provide more detailed description of the
    elements in each category in the following sections.  Extensibility
    is very important for a service creation language. Section 9 defines
    how to write LESS extensions. Several commonly used extensions are
    defined in the following sections. Section 17 provides service
    examples written in LESS. Section 19 shows the XML schema of the
    language.

 1.1 Conventions of This Document




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    In this document, the key words "MUST", "MUST NOT", "REQUIRED",
    "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
    and "OPTIONAL" are to be interpreted as described in RFC 2119 [1] and
    indicate requirement levels for compliant LESS implementations.


         Some paragraphs are indented, like this; they give
         motivations of design choices, advice to implementors, or
         thoughts on future development of or extensions to LESS.
         They are not essential to the specification of the
         language, and are non-normative.

 2 LESS design decisions

    The goal of the language is to allow end users to program their own
    communication services with little training in a graphical service
    creation environment. To achieve the goal, the language must
    represent a high-level abstraction of communication behaviors. The
    elements in the language must have semantic meanings. The language
    has to be simple and safe. The Call Processing Language (CPL) [2] has
    all the above features.  However, CPL is originally designed for
    network servers, such as SIP proxy servers. It lacks of the functions
    for end system services, e.g., accepting calls, making outgoing
    calls, and interacting with users.  CPL does not have variables,
    which is very important for call decision making and user
    interactions. We have LESS inherit the basic structure and many
    elements from CPL and enhance it with more elements for end system
    services.

    In this section, we first provide the high-level structure of LESS.
    We then analyze the simplicity and safety of the design rules.

 2.1 High-level Structure

    As shown in Figure 1, we consider that every service starts with a
    trigger invoked, such as an incoming call, an event notification, a
    user interaction event, or a timer event. The service will then check
    its current context, such as user status, device status, and the
    status related to the trigger. We name the check points as switches,
    which can branch call decisions. Once a service gets its matching
    condition, it will perform pre-defined actions, e.g., accepting an
    incoming call, holding an existing call, or sending an instant
    message. We use modifiers to provide parameters to actions, e.g.,
    media modifier to define media information of a call action.
    Additional actions may get performed based on the result of an
    action.





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                                  +--------+
                                  |        +-------+
                                  |modifier|       |
                                  |        |<------+
                       *          +---+----+
                      * *             |
                     *   *            V
     =========      *     *        +------+
    ( trigger )---* switch*------|action|---+
     =========      *     *        +--+---+   |
                     *   *                    |
                      * *<--------------------+
                       *


    Figure 1: The high-level structure of LESS


    The above high-level abstraction makes LESS having a tree-like
    structure, as shown in Figure 2. The tree-like structure makes LESS
    easy to analyze and safe for service programming.


 2.2 Simplicity

    "The fewer concepts to understand in a language the better" [13],
    though, in some cases two smaller concepts might be simpler and more
    flexible than one more powerful but complicated concept. For example,
    separating commonly used action arguments, such as people's contact
    locations, as modifiers is better than putting the arguments into
    every action.

    "Simplicity enters in four disguises: uniformity (rules are few and
    simple), generality (a small number of general functions provide as
    special cases of more specialized functions), familiarity (familiar
    symbols and usages are adopted whenever possible), and brevity
    (economy of expression is sought)" [14]. For LESS, we consider
    analyzability is more important than brevity because LESS is an XML-
    based language designed for communication services and has people
    without programming experience as its target users.  In communication
    service creation, users may encounter feature interaction [15]
    problems, how to analyze and solve feature interactions is essential
    for users to create usable services. We discuss the familiarity,
    generality, uniformity, and analyzability of LESS below.

 2.2.1 Familiarity




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          +----------+
          | incoming | (trigger)
          +-----+----+
                |
                |
     +----------+------------+
     |Is the sender's address| (switch)
     |  sip:bob@example.com? |
     +----------**-----------+
               /  |
             YES   NO
             /      |
     +------*    +---*-----------------------+
     |accept|    |Is the priority of the call| (switch)
     +------+    |  greater than 'normal'?   |
     (action)    +--------**-----------------+
                         /  |
                       YES   NO
                       /      |
                  +---*-+   +--*------------------+
                  |alert|   |redirect to voicemail|
                  +-----+   +---------------------+
                  (action)    (action)


    Figure 2: Sample decision tree


    The familiarity requires a language not to violate common use of
    notation.  We choose to use the Extensible Markup Language (XML) [3]
    to define LESS, uses the datatypes defined in XML schema. By this
    way, the elements defined in LESS all have semantic meaning and easy
    for users to understand and remember.

 2.2.2 Generality

    The generality requires a language to have a small number of general
    elements.  The special elements of the language can be introduced by
    specializing the general elements. As illustrated in Section 2.1,
    LESS has only four kinds of elements, namely triggers, switches,
    actions, and modifiers. Every new element defined in LESS extensions
    must fall in one kind of the elements. In another words, in LESS's
    XML schema, LESS will have four basic abstract elements, namely
    'trigger', every element must be a substitutionGroup of one of the
    four abstract elements.

 2.2.3 Uniformity



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    The uniformity requires a language with few and simple rules. There
    are only four rules in LESS. The rules can be summarized below:

         Trigger rule: A LESS script gets invoked if and only if one of
              its triggers get matched. A trigger must be the root of a
              decision tree.  Two triggers with the same name and
              attributes cannot appear in the same script.

         Switch rule: Only switches can branch call decisions. One switch
              have no more than two branches. A switch must be a child of
              a trigger or another switch in a decision tree.

         Action rule: Only actions can change call status and call
              context and only actions can be LESS decision tree leaves.
              There can be subsequent actions after one action. No
              triggers can follow an action.

         Modifier rule: A modifier can only be used as the parent element
              of actions to enforce the actions.

 2.2.4 Analyzability

    Another aspect of language simplicity is how easy to analyze a
    program written by the language. For LESS, we are more interested in
    how LESS handling feature interaction problems in communication
    services. As discussed in our technical report "Feature Interactions
    in Internet Telephony End Systems" [15], we can handle feature
    interaction problems among LESS scripts by the action conflict tables
    and the tree merging algorithm defined in the technical report. The
    process is straight-forward, and can also help to solve detected
    interactions.

 2.3 Safety

    Since LESS will be used by people without programming experience, we
    may expect errors that seem naive by experienced programmers. We
    should also expect that people may use third-party created malicious
    service scripts.  The language design should help people to prevent
    errors and protect people from malicious scripts. The error
    prevention mechanisms for LESS fall into two categories, one is to
    put restrictions on the language itself, the other is to put
    restrictions on LESS engines.  We are more interested in the
    restrictions on the language itself since that is directly related to
    the language design. The restrictions on LESS engines may cause
    service portability problem so we should try to prevent errors in the
    language design whenever possible.

 2.3.1 Type safety



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    Type checking is a very effective way in catching programming errors,
    from the trivial errors, such as misspelled identifiers, to the
    fairly deep errors, such as violations of data structure invariants.

    LESS is an XML-based language and uses XML schema [4] to define its
    elements. "The strong typing mechanism in XML Schema, along with the
    large set of intrinsic types and the ability to create user-defined
    types, provides for a high level of type safety in instance
    documents. This feature can be used to express more strict data type
    constraints, such as those of attribute values, when using XML Schema
    for validation." [4]

    In LESS, there are no user defined variables so only static type
    checking is needed. There are many advantages to have a statically
    type-checked language. Static type checking can provide earlier, and
    usually more accurate information on programmer errors. It can
    eliminate the need for run-time checks, which may slow program
    execution. Statically type-checked language may be less expressive
    than dynamically type-checked language, however, since LESS is not
    designed to handle all communication services and targets to end
    users, safety is more important than expressiveness.

 2.3.2 Control flow safety

    LESS has a tree-like structure for call decision making. LESS does
    not allow a tree node to back-reference to its ancestors or itself.
    This means there is no loop or recursion in LESS scripts, and will
    exclude the possibility of non-terminating or non-decidable LESS
    scripts.  However, LESS still provides some mechanisms for repeated
    events handling.  The timer trigger can get invoked periodically. The
    lookup modifier implies that follow-up actions are applied to every
    location in the result set.

    Run-time feature interactions may confuse users.  The LESS trigger
    rule ensures that a specific trigger can appear no more than once in
    a LESS script thus helps to avoid run-time feature interactions in
    the LESS script. The LESS service creation environment should help
    users to merge multiple service scripts into one as illustrated in
    the technical report on feature interaction handling in LESS [15].

 2.3.3 Memory access

    A language can be described as unsafe in that the language allows
    some means to access memory directly. In LESS, there are no pointers,
    no direct memory accesses, and even no user-defined variables. LESS
    has maximum string length defined in its XML schema for every element
    with string type to prevent buffer overflow attack. If a user put a
    very long string in a service script, the service script will be



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    considered invalid when checking against the LESS XML schema.

 2.3.4 LESS engine safety

    LESS engine developers can do several things to enhance the safety of
    LESS scripts. The developers must make sure that every trigger has
    default behaviors defined.  If a trigger gets invoked in a LESS
    engine, but there is no actions defined for the matching context, the
    LESS engine must perform the default actions for that trigger. This
    ensures every LESS script is decidable.

    LESS is different from CPL [2] when dealing with user trustiness. CPL
    is designed for running on signaling servers, such as SIP proxy
    servers.  The safety consideration for CPL ensures that semi-trusted
    users cannot create malicious or incompetent service scripts to
    interrupt other users' services, including crashing the server,
    revealing security-sensitive information, and causing denial of
    service. While LESS is used on users' end devices, usually, it does
    not need to handle the interference of other users.  LESS engine need
    to ensure safe resource usages, such as CPU usage. It needs to define
    how deep a decision tree can be, what is the minimum interval for
    timer trigger, and whether it can control multimedia devices.

 2.3.5 Using third-party created or auto-generated service scripts

    Sometimes, end users may not be aware of a new service or they may
    not know how to create a service, the service scripts auto-generated
    by feature learning, or created by third-parties, may bring great
    conveniences to users. However, end users have to check the safety of
    the third-party created or auto-generated scripts, for example, to
    make sure that the scripts will not crash their systems or forward
    their calls to unwanted parties.

    The safety consideration discussed in previous sections can be
    applied to third-party or auto-generated service scripts. In
    addition, the simplicity and the tree-like structure of LESS make it
    viable to convert any valid LESS scripts into graphical
    representation of decision trees.  This is a big advantage of LESS
    for end users to do safety checking.  Users do not have to check LESS
    programs line by line, instead, they can watch the graphical
    representation and easily find out what actions a service script will
    perform.

 3 LESS elements

    As we discussed earlier, LESS has four kinds of elements, namely
    triggers, switches, actions, and modifiers.




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    A trigger is an entry point to every service. It is the same as the
    toplevelactions defined in CPL. The basic LESS definition has two
    triggers, "incoming" (Section 5.1.1) and "timer" (Section 5.1.2).
    Note that we do not have "outgoing" trigger, which is defined in CPL.
    Because in end systems, an outgoing call is usually triggered by some
    user interactions, e.g., pressing a call button. This is different
    from that in an outbound server, in which "outgoing" triggered by
    receiving an outgoing call signaling message. We defined user
    interaction extension, which has one trigger, "UI:command" (Section
    12.1.1).  The event handling extension has two triggers,
    "Event:notification" (Section 14.1.2) and , "Event:subscription"
    (Section 14.1.1).  The instant messaging extension has one trigger,
    "Message:message" (Section 13.1.1).

    Switches branch call decisions. This is the same as CPL switches.
    The basic LESS definition has six switches, namely "time-switch"
    (Section 5.2.1), "address-switch" (Section 5.2.2), "language-switch"
    (Section 5.2.5), "priority-switch" (Section 5.2.3), "string-switch"
    (Section 5.2.4), and "status-switch" (Section 5.2.6). The location-
    based service extension has two switches, "where-switch" (Section
    15.1.1) and "where-relation-switch" (Section 15.1.2).  The event
    handling extension has one switch, "event-switch" (Section 14.2.1).

    Actions represent users' decision for trigger handling. This is
    similar to CPL actions, but we allow multiple actions be executed in
    parallel and in sequential. Each action has a "next" output. Actions
    in an action's "next" output will be executed after the action. If
    multiple actions have the same parent tag, they are executed in
    parallel.

    The basic LESS definition has six signaling actions, namely "accept"
    (Section 5.4.1), "reject" (Section 5.4.2), "redirect" (Section
    5.4.3), "authenticate" (Section 5.4.4), "call" (Section 5.4.5), and
    "terminate" (Section 5.4.6).  It also has three non-signaling
    actions, "mail" (Section 5.4.7) "log" (Section 5.4.8), and "wait"
    (Section 5.4.9).

    We defined a mid-call handling extension. It has two actions,
    "Midcall:transfer" (Section 11.1.1), and "Midcall:merge" (Section
    11.1.2).  The user interaction extension has two actions, "UI:alert"
    (Section 12.2.1).  "UI:getinput" (Section 12.2.2).  The instant
    messaging extension has one action, "IM:sendmsg" (Section 13.2.1).
    The event handling extension has five actions, "Event:subscribe"
    (Section 14.3.4), "Event:notify" (Section 14.3.5), "Event:approve"
    (Section 14.3.1), "Event:deny" (Section 14.3.2), and "Event:defer"
    (Section 14.3.3).  The queue handling extension has two actions,
    "Queue:enqueue" (Section 16.1.1), and "Queue:dequeue" (Section
    16.1.2).



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    Modifiers provide action parameters. We have three modifiers defined
    in basic LESS definition, namely "location" (Section 5.3.1), "lookup"
    (Section 5.3.2), and "remove-location" (Section 5.3.3).  In media
    handling extension, we defined "media" (Section 10.1.1) modifier.

 4 Variables

    LESS does not allow user-defined variables, however, it allows
    several pre-defined variables to retrieve system information, user
    information, agent information, trigger information, and action
    information.  The variables can be used in descriptive messages, such
    as the reason parameter of a reject message. We use the format
    'variable-name' to represent a variable in a LESS script. For
    example, in a "reject" action, we can provide its reason parameter as
    below.


      <reject code="486" reason="Sorry, I am {user.activity}"



 4.1 System information

         system.bandwidth represents the bandwidth of the end system
              running the script.

 4.2 User information

         user.presence represents script owner's online/offline
              information.

         user.activity represents script owner's current activity.
              Activity values are defined as in the Rich Presence
              Extensions to the Presence Information Data Format (RPID)
              [5].

         user.mood represents script owner's current mood. Mood values
              are defined as in RPID.

         user.location represents script owner's physical location.

         user.language represents script owner's preferred language.

 4.3 Agent information

         agent.number-of-calls represents the number of existing calls in
              the user agent running the script.




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         agent.media-capabilities represents the media capabilities in
              the user agent running the script.

 4.4 Trigger information

         trigger.origin represents the originator of a trigger's
              signaling message.

         trigger.destination represents the destination of a trigger's
              signaling message.

         trigger.priority represents the priority of a trigger's
              signaling message.

         trigger.timestamp represents when the signaling message is
              received.

         trigger.subject represents the subject of a trigger's signaling
              message.

 4.5 Action information

         action.last-action-result represents the return value of last
              actions.  Every action may return a value. In this
              document, if the return value is not specified, the return
              value will be empty.

 5 Basic LESS elements

 5.1 Triggers

 5.1.1 "incoming" trigger

    The "incoming" trigger is the same as that defined in CPL [2],
    Section 2.1.

 5.1.2 "timer" trigger

    The "timer" trigger is to handle timer-based events, e.g.,
    automatically making an outgoing call at a specific time. The "timer"
    trigger has the same attributes as those defined in "time-switch"
    (Section 5.2.1).  Their syntax is shown in Figure 3.









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       Trigger:  "timer"
    Parameters:  "dtstart"     Start of interval (RFC 2445 DATE-TIME)
                 "dtend"       End of interval (RFC 2445 DATE-TIME)
                 "duration"    Length of interval (RFC 2445 DURATION)
                 "freq"        Frequency of recurrence ("secondly",
                               "minutely", "hourly", "daily",
                               "weekly", "monthly", or "yearly")
                 "interval"    How often the recurrence repeats
                 "until"       Bound of recurrence (RFC 2445 DATE-TIME)
                 "count"       Number of occurrences of recurrence
                 "bysecond"    List of seconds within a minute
                 "byminute"    List of minutes within an hour
                 "byhour"      List of hours of the day
                 "byday"       List of days of the week
                 "bymonthday"  List of days of the month
                 "byyearday"   List of days of the year
                 "byweekno"    List of weeks of the year
                 "bymonth"     List of months of the year
                 "wkst"        First day of the work week
                 "bysetpos"    List of values within
                               set of events specified


    Figure 3: Syntax of the "timer" trigger



 5.2 Switches

 5.2.1 "time-switch"

    The "time-switch" is the same as that defined in CPL [2], Section
    4.4.

 5.2.2 "address-switch"

    The "address-switch" is the same as that defined in CPL [2], Section
    4.1.

 5.2.3 "priority-switch"

    The "priority-switch" is the same as that defined in CPL [2], Section
    4.5.

 5.2.4 "string-switch"

    The "string-switch" is the same as that defined in CPL [2], Section



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    4.2.

 5.2.5 "language-switch"

    The "language-switch" is the same as that defined in CPL [2], Section
    4.3.

 5.2.6 "status-switch"

    Status-switches allow a LESS script to make decisions based on the
    status of the script owner, or other people whose status can be
    acquired.  The syntax of "status-switch" is summarized in Figure 4.


          Node:  "status-switch"
       Outputs:  "status"         Specific status to match
    Parameters:  "uri"            The principal's URI
                 "status-name"    The name of the status to check. Available
                                  values are "active-calls", "activity",
                                  "mood", and "presence".

        Output:  "status"
    Parameters:  "greater"        Used for "active-calls"
                 "less"           Used for "active-calls"
                 "equal"          Used for "active-calls"
                 "is"             Exact match, not for "active-calls"
                 "contains"       Not for "active-calls"


    Figure 4: Syntax of the "status-switch" node



    "status-switch" takes two parameter. "uri" indicates the URI of the
    principal for status checking. If omited, the principal for checking
    will be the script owner. "status-name" indicates what status to
    check. It has four possible values:

         "active-calls" checks for ongoing active calls.

         "presence" checks for online/offline status of the principal.

         "mood" checks for the mood of the principal.

         "activity" checks for the activity of the principal.

    The "status" output takes five parameters, indicating different
    conditions to match. The "greater", "less", and "equal" can only be



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    used for "active-calls", indicating whether the number of active
    calls is greater than, less than, or equal to a specific value.  The
    "is" parameter takes a list of strings for its value. User status
    MUST equal to all the strings in the list for being matched.  The
    "contains" parameter also takes a list of strings for match.  if user
    status equals to any string in the list, the switch get matched.

 5.3 Modifiers

 5.3.1 "location" Modifier

    The "location" modifier is the same as that defined in CPL [2],
    Section 5.1.

 5.3.2 Location Lookup

    The "lookup" modifier is the same as that defined in CPL [2], Section
    5.2.

 5.3.3 Location Removal

    The "remove-location" modifier is the same as that defined in CPL
    [2], Section 5.3.

 5.4 Actions

    As we discussed before, LESS allows multiple actions get executed
    sequentially or in parallel. Every LESS action will have a default
    output "next". In the following sections, we will omit this default
    output for the syntax of actions.

 5.4.1 "accept"

    "accept" actions cause the user agent to accept an incoming call.
    Their syntax is shown in Figure 5.


                                 Node:  "accept"
                              Outputs:  None
                            Next node:  None
                           Parameters:  None


    Figure 5: Syntax of the "accept" node



    There is no parameters for the "accept" action. We can use "media"



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    modifier to change "accept" action's media parameters, as described
    in Section 10.1.1.

 5.4.2 "reject"

    The "reject" modifier is the same as that defined in CPL [2], Section
    6.3.

 5.4.3 "redirect"

    The "redirect" modifier is the same as that defined in CPL [2],
    Section 6.2.

 5.4.4 "authenticate"

    "authenticate" actions cause user agents to authenticate local users
    or remote users.  Their syntax is shown in Figure 6.


          Node:  "authenticate"
       Outputs:  "success"       Next node if authentication succeeded
                 "failure"       Next node if authentication failed
    Parameters:  "method"        Authentication method to use. Possible values
                                 are "basic" and "digest".
                 "realm"         The realm for authentication challenge.
                 "user"          Required user for authentication.
                 "target"        Which party to authenticate. Possible values
                                 are "remote" and "local".

        Output:  "success"
    Parameters:  none

        Output:  "failure"
    Parameters:  none


    Figure 6: Syntax of the "authenticate" node



    "authenticate" action takes four arguments: "method", "realm", "user"
    and "target". The default value for "method" is "digest", which
    representing digest authentication.

    The action has two outputs, "success" and "failure", handles the
    situation under which the authentication succeeds or fails,
    accordingly.




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 5.4.5 "call"

    "call" actions cause the user agent to make an outgoing call.  Their
    syntax is shown in Figure 7.


          Node:  "call"
       Outputs:  "accepted"     Next node if call attempt get accepted.
                 "busy"         Next node if call attempt returned "busy".
                 "failure"      Next node if call attempt failed.
                 "noanswer"     Next node if call attempt was not
                                answered before timeout.
                 "redirection"  Next node if call attempt was redirected.
    Parameters:  "timeout"      Time to try before giving up call attempt.

        Output:  "accepted"
    Parameters:  none

        Output:  "busy"
    Parameters:  none

        Output:  "noanswer"
    Parameters:  none

        Output:  "failure"
    Parameters:  none

        Output:  "redirection"
    Parameters:  none


    Figure 7: Syntax of the "call" node



    The "call" action has one parameter, "timeout", which specifies the
    time, as a positive integer number of seconds, to wait for the call
    attempt. We can also use "media" modifier to change "call" action's
    media parameters, as described in Section 10.1.1.

    The "call" action has five outputs. The "accepted" is followed if the
    call was accepted; the "busy" is followed if the call was busy; the
    "noanswer" is followed if the call was not answered before the
    "timeout" parameter expired; the "failure" is followed if the call
    failed for any other reason; the "redirection" is followed if the
    call was redirected.

 5.4.6 "terminate"



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    "terminate" actions cause the user agent to terminate one or more
    ongoing sessions or call attempts.  Their syntax is shown in Figure
    8.


             Node:  "terminate"
          Outputs:  None
        Next node:  None
       Parameters:  "uri"        Select calls to terminate based on
                                 the "uri" list.
                    "subject"    Select calls to terminate based on
                                 the "subject" list.
                    "calls"      Possible values are "all", "last",
                                 and "this". Default value is "this".


    Figure 8: Syntax of the "terminate" node



    There are three parameters for the "terminate" action, which define
    how to select calls to terminate. If "uri" parameter presented, all
    calls to one of the "uri" values will get terminated. If "subject"
    parameter presented, all calls with one of the "subject" values will
    get terminated. If the "calls" parameter is "all", all calls matching
    "uri" and "subject" parameters will get terminated, if it is "last",
    the last established session will get terminated, if it is "this",
    the calls associated with the trigger event of the script will get
    terminated.

 5.4.7 "mail"

    The "mail" action is the same as that defined in CPL [2], Section
    7.1.

 5.4.8 "log"

    The "log" action is similar to that defined in CPL [2], Section 7.2.
    But we added a new parameter for recording a call. The recording
    parameter makes it easy to associate a log with a recorded call.
    Their new syntax is shown in Figure 9.










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               Node:  "log"
            Outputs:  None
          Next node:  Any node
         Parameters:  "name"       Name of the log file to use
                      "comment"    Comment to be placed in log file
                      "recording"  The URI to place recording files


    Figure 9: Syntax of the "log" node



 5.4.9 "wait"

    "wait" actions cause the user agent to perform subsequent actions in
    the "next" output after a duration of time.  Their syntax is shown in
    Figure 10.


                          Node:  "wait"
                       Outputs:  None
                     Next node:  Any node
                    Parameters:  "duration"  Time to wait


    Figure 10: Syntax of the "wait" node



 6 Subactions and Ancillary Information

    Subactions and ancillary information are the same as those defined in
    CPL Section 8 and Section 9.

 7 Security Considerations

    LESS shares the same security considerations as CPL, as defined in
    CPL document [2], Section 13.

 8 IANA Considerations

    This document registers a new MIME type, application/less+xml, and a
    new URN per RFC 2141 [6], RFC 2648 [7], and RFC 3688 [8].

    The XML namespace urn:ietf:params:xml:ns:less will only refer to the
    version of LESS in this document and will not change.  Any LESS
    enhancements MUST be made by extensions and MUST have different



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    namespaces.

 8.1 URN Sub-Namespace Registration for urn:ietf:params:xml:ns:less

         URI: urn:ietf:params:xml:ns:less

         Registrant Contact: Xiaotao Wu <xiaotaow@cs.columbia.edu
              Henning Schulzrinne <hgs@cs.columbia.edu

         XML:

               BEGIN
               <?xml version="1.0"?
               <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
                   "http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd"
               <html xmlns="http://www.w3.org/1999/xhtml"
               <head
                 <meta http-equiv="content-type"
                    content="text/html;charset=iso-8859-1"/
                 <titleLanguage for End System Services Namespace</title
               </head
               <body
                 <h1Namespace for the Language for End System Services</h1
                 <h2urn:ietf:params:xml:ns:less</h2
                 <p<a href="[[[URL of published RFC]]]"RFCXXXX</a.</p
               </body
               </html
               END


 8.2 Schema registration

    This specification registers XML Schema for LESS, as per the
    guidelines in [8].

         URI: urn:ietf:params:xml:schema:less

         Registrant contact:
              Xiaotao Wu <xiaotaow@cs.columbia.edu
              Henning Schulzrinne <hgs@cs.columbia.edu

         XML: The XML can be found in Section 19.1.

 8.3 MIME Registration

    As an XML type, LESS's MIME registration conforms with "XML Media
    Types," RFC 3023 [9].




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         MIME media type name: application

         MIME subtype name: less+xml

         Mandatory parameters: none

         Optional parameters: charset
              As for application/xml in RFC 3023.

         Encoding considerations: As for application/xml in RFC 3023.

         Security considerations: See Section 7, and Section 10 of RFC
              3023.

         Interoperability considerations: Different user agents may use
              incompatible address types. However, all potential
              interoperability issues should be resolvable at the time a
              script is uploaded; there should be no interoperability
              issues which cannot be detected until runtime.

         Published specification: This document.

         Applications which use this media type: SIP user agents.

         Additional information:

              Magic number: None

              File extension: .less or .xml

              Macintosh file type code: "TEXT"

         Person and e-mail address for further information:
              Xiaotao Wu <xiaotaow@cs.columbia.edu
              Henning Schulzrinne <hgs@cs.columbia.edu

         Intended usage: COMMON

         Author/Change Controller: The IETF.

 9 LESS Extensions

    User agents MAY support additional LESS features beyond those listed
    in this document. LESS extensions are indicated by XML namespaces
    [10]. Every extension MUST have an appropriate XML namespace assigned
    to it.  The XML namespace of the extension MUST be different from the
    XML namespace defined in Section 15.2. The extension MUST NOT change
    the syntax or semantics of the basic LESS schema defined in this



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    document. All XML tags and attributes that are part of the extension
    MUST be appropriately qualified so as to place them within that
    namespace.

    A LESS script SHOULD NOT specify any namespaces it does not use. For
    compatibility with non-namespace-aware parsers, a LESS script MAY
    omit the base LESS namespace for a script which does not use any
    extensions.

    A LESS server MUST reject any script which contains a reference to a
    namespace which it does not understand. It MUST reject any script
    which contains an extension tag or attribute which is not qualified
    to be in an appropriate namespace.

    In the XML schema of LESS, we introduce four abstract elements,
    namely `trigger', `switch', `action', and `modifier', which
    accordingly have the abstract type `TriggerType', `SwitchType',
    `ActionType', and 'ModifierType'. Any trigger in a LESS extension
    MUST be defined as the substitutionGroup of the abstract `trigger'
    element, and has the type extended from the `TriggerType'.  Any
    switch in a LESS extension MUST be defined as the substitutionGroup
    of the abstract `switch' element, and has the type extended from the
    `SwitchType'. Any action in a LESS extension MUST be defined as the
    substitutionGroup of the abstract `action' element, and has the type
    extended from the `ActionType'.  Any modifier in a LESS extension
    MUST be defined as the substitutionGroup of the abstract `modifier'
    element, and has the type extended from the `ModifierType'.

    We defined several commonly used extensions that are very important
    for LESS-based services as below.

 10 Media handling extension

    Media handling extensions define the elements that can manipulate
    session media information.

 10.1 Modifiers

 10.1.1 "Media:media" Modifier

    "Media:media" modifiers specify what media to use for an signaling
    action, such as "accept" and "call", as well as the parameters of the
    media.  Their syntax is shown in Figure 11.








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          Node:  "Media:media"
       Outputs:  None           (Next node follows directly)
     Next node:  Any node
    Parameters:  "media"        A list of medias. Possible values are "audio",
                                and "video".
                 "input"        The source of input. It can be "microphone",
                                for audio, "camera" for video, or a URL
                                to a media file.
                 "mode"         Possible values are "sendonly", "recvonly",
                                "sendrecv", and "inactive".
                 "codec"        The codec used for the media.


    Figure 11: Syntax of the "Media:media" node



 10.2 Actions

 10.2.1 "Media:mediaupdate" Action

    "Media:mediaupdate" actions cause the user agent to change the media
    setup for an ongoing session.  Their syntax is shown in Figure 12.


                              Node:  "mediaupdate"
                           Outputs:  None
                         Next node:  None
                        Parameters:  None


    Figure 12: Syntax of the "mediaupdate" node



    There is no parameters for the "mediaupdate" action. We can use
    "media" modifier to change "mediaupdate" action's media parameters,
    as described in Section 10.1.1.  "Media:mediaupdate" actions can be
    used to handle some mid-call handling services, such as "mute" and
    "hold".

 10.3 IANA Considerations

    This extension registers a new URN per RFC 2141 [6], RFC 2648 [7],
    and RFC 3688 [8].

    The XML namespace urn:ietf:params:xml:ns:less:media will only refer



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    to the version of LESS media extension in this document and will not
    change.  Any other LESS enhancements MUST be made by extensions and
    MUST have different namespaces.

 10.3.1 URN Sub-Namespace Registration for
    urn:ietf:params:xml:ns:less:media

         URI: urn:ietf:params:xml:ns:less:media

         Registrant Contact: Xiaotao Wu <xiaotaow@cs.columbia.edu
              Henning Schulzrinne <hgs@cs.columbia.edu

         XML:

               BEGIN
               <?xml version="1.0"?
               <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
                   "http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd"
               <html xmlns="http://www.w3.org/1999/xhtml"
               <head
                 <meta http-equiv="content-type"
                    content="text/html;charset=iso-8859-1"/
                 <titleMedia Extension of the Language for End System Services Namespace</title
               </head
               <body
                 <h1Namespace for the Media Extension of the Language for End System Services</h1
                 <h2urn:ietf:params:xml:ns:less:media</h2
                 <p<a href="[[[URL of published RFC]]]"RFCXXXX</a.</p
               </body
               </html
               END


 10.3.2 Schema registration

    This specification registers XML Schema for LESS, as per the
    guidelines in [8].

         URI: urn:ietf:params:xml:schema:less:media

         Registrant contact:
              Xiaotao Wu <xiaotaow@cs.columbia.edu
              Henning Schulzrinne <hgs@cs.columbia.edu

         XML: The XML can be found in Section 19.2.

 10.3.3 MIME Registration




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    LESS Media extension has the same MIME type as LESS as defined in
    Section 8.3.

 11 Mid-call Handling extension

    Mid-call handling actions can manipulate ongoing sessions. As we
    discussed before, "Media:mediaupdate" can handle "mute" and "hold"
    services. This extension defines two new actions, namely
    "Midcall:transfer" and "Midcall:merge".

 11.1 Actions

 11.1.1 "Midcall:transfer" Action

    "Midcall:transfer" actions cause the user agent to transfer existing
    calls to another user.  Their syntax is shown in Figure 13.


          Node:  "Midcall:transfer"
       Outputs:  "accepted"          Next node if "transfer" was accepted.
                 "busy"              Next node if "transfer" returned "busy".
                 "failure"           Next node if "transfer" failed.
                 "noanswer"          Next node if "transfer" was not
                                     answered before timeout.
                 "redirection"       Next node if "transfer" was redirected.
    Parameters:  "timeout"           Time to try before giving up "transfer".

        Output:  "accepted"
    Parameters:  none

        Output:  "busy"
    Parameters:  none

        Output:  "noanswer"
    Parameters:  none

        Output:  "failure"
    Parameters:  none

        Output:  "redirection"
    Parameters:  none


    Figure 13: Syntax of the "Midcall:transfer" node



    The "Midcall:transfer" action takes the same parameter and outputs as



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    "call" action, as defined in Section 5.4.5.

 11.1.2 "Midcall:merge" Action

    "Midcall:merge" actions will merge multiple calls into an end system
    hosted conference. By default, audio streams will be mixed and sent
    to all the call participants. Video streams are forwarded to all the
    call participants. If there are held or muted calls, the hold and
    mute status are kept.  Their syntax is shown in Figure 14.


          Node:  "Midcall:merge"
       Outputs:  None
     Next node:  None
    Parameters:  "uri"            Select calls to merge based on the "uri" list.
                 "subject"        Select calls to merge based on
                                  the "subject" list.


    Figure 14: Syntax of the "Midcall:merge" node



    There are two parameters for the "Midcall:merge" action, which define
    how to select calls to merge. If "uri" parameter presented, all calls
    to one of the "uri" values will be merged. If "subject" parameter
    presented, all calls with the one of the "subject" values will be
    merged. If further calls want to get merged into an existing end
    system hosted conference, users can use any value in "uri" list or
    "subject" list to refer to an existing conference.

 11.2 IANA Considerations

    This extension registers a new URN per RFC 2141 [6], RFC 2648 [7],
    and RFC 3688 [8].

    The XML namespace urn:ietf:params:xml:ns:less:midcall will only refer
    to the version of LESS mid-call handling extension in this document
    and will not change. Any other LESS enhancements MUST be made by
    extensions and MUST have different namespaces.

 11.2.1 URN Sub-Namespace Registration for
    urn:ietf:params:xml:ns:less:midcall

         URI: urn:ietf:params:xml:ns:less:midcall

         Registrant Contact: Xiaotao Wu <xiaotaow@cs.columbia.edu
              Henning Schulzrinne <hgs@cs.columbia.edu



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         XML:

               BEGIN
               <?xml version="1.0"?
               <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
                   "http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd"
               <html xmlns="http://www.w3.org/1999/xhtml"
               <head
                 <meta http-equiv="content-type"
                    content="text/html;charset=iso-8859-1"/
                 <titleMid-call Handling Extension of the Language for End System Services Namespace</title
               </head
               <body
                 <h1Namespace for the Mid-call Handling Extension of the Language for End System Services</h1
                 <h2urn:ietf:params:xml:ns:less:midcall</h2
                 <p<a href="[[[URL of published RFC]]]"RFCXXXX</a.</p
               </body
               </html
               END


 11.2.2 Schema registration

    This specification registers XML Schema for LESS, as per the
    guidelines in [8].

         URI: urn:ietf:params:xml:schema:less:midcall

         Registrant contact:
              Xiaotao Wu <xiaotaow@cs.columbia.edu
              Henning Schulzrinne <hgs@cs.columbia.edu

         XML: The XML can be found in Section 19.2.

 11.2.3 MIME Registration

    LESS Media extension has the same MIME type as LESS as defined in
    Section 8.3.

 12 User Interaction extension

    User Interaction extension handles user inputs and perform actions
    for alerting users and getting user inputs. It has one trigger and
    two actions defined.

 12.1 Triggers

 12.1.1 "UI:command" Trigger



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    "UI:command" handles user invoked commands, such as pressing call
    button, hold button, or transfer button.  Their syntax is shown in
    Figure 15.


                 Trigger:  "UI:command"
              Parameters:  "command"     Command name to match.


    Figure 15: Syntax of the "UI:command" trigger



    "UI:command" trigger takes one parameter, "command", to check the
    command to match. Commands can be "call", "hold", "mute", "transfer",
    or any other commands users may perform.  Usually, a command is
    associated with a user interface button.

 12.2 Actions

 12.2.1 "UI:alert" Action

    "UI:alert" actions play alerting messages.  Their syntax is shown in
    Figure 16.


          Node:  "UI:alert"
       Outputs:  "timeout"   Next node if alerting time exceeds that
                             specified in "duration" parameter.
    Parameters:  "duration"  Time to play alerting message before
                             stopping alert.
                 "priority"  Priority of alerting. Possible values
                             are "emergency", "urgent", "normal",
                             and "non-urgent".
                 "icon"      The icon to display on the alerting interface.
                 "message"   The message to display on the alerting interface.
                 "style"     Possible alerting styles. Can be a combination of
                             "vibrate", "sound", "flash",
                             and "text". By default, it is "sound".
                 "input"     Play a file as specified in the "input" URI.

        Output:  "timeout"
    Parameters:  none


    Figure 16: Syntax of the "UI:alert" node





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 12.2.2 "UI:getinput" Action

    "UI:getinput" actions acquire users' input.  Their syntax is shown in
    Figure 17.


            Node:  "UI:getinput"
         Outputs:  "noanswer"                                      Next node if no input after the time

 specified in "timeout" parameter.
      Parameters:  "timeout"                                       Time to wait for user input.
                   "source"                                        Input source, possible values are

 "screen" and "sound".
                   "target"                                        Get input from "local" or "remote" user.
    Return value:  Return a text string acquired from user input.

          Output:  "noanswer"
      Parameters:  none


    Figure 17: Syntax of the "UI:getinput" node



 12.3 IANA Considerations

    This extension registers a new URN per RFC 2141 [6], RFC 2648 [7],
    and RFC 3688 [8].

    The XML namespace urn:ietf:params:xml:ns:less:ui will only refer to
    the version of LESS mid-call handling extension in this document and
    will not change. Any other LESS enhancements MUST be made by
    extensions and MUST have different namespaces.

 12.3.1 URN Sub-Namespace Registration for urn:ietf:params:xml:ns:less:ui

         URI: urn:ietf:params:xml:ns:less:ui

         Registrant Contact: Xiaotao Wu <xiaotaow@cs.columbia.edu
              Henning Schulzrinne <hgs@cs.columbia.edu

         XML:










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               BEGIN
               <?xml version="1.0"?
               <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
                   "http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd"
               <html xmlns="http://www.w3.org/1999/xhtml"
               <head
                 <meta http-equiv="content-type"
                    content="text/html;charset=iso-8859-1"/
                 <titleUser Interaction Extension of the Language for End System Services Namespace</title
               </head
               <body
                 <h1Namespace for the User Interaction Extension of the Language for End System Services</h1
                 <h2urn:ietf:params:xml:ns:less:ui</h2
                 <p<a href="[[[URL of published RFC]]]"RFCXXXX</a.</p
               </body
               </html
               END


 12.3.2 Schema registration

    This specification registers XML Schema for LESS, as per the
    guidelines in [8].

         URI: urn:ietf:params:xml:schema:less:ui

         Registrant contact:
              Xiaotao Wu <xiaotaow@cs.columbia.edu
              Henning Schulzrinne <hgs@cs.columbia.edu

         XML: The XML can be found in Section 19.2.

 12.3.3 MIME Registration

    LESS Media extension has the same MIME type as LESS as defined in
    Section 8.3.

 13 Instant Messaging extension

 13.1 Triggers

 13.1.1 "IM:message" Trigger

    "IM:message" handles incoming instant messages.  Their syntax is
    shown in Figure 18.





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                            Trigger:  "IM:message"
                         Parameters:  None


    Figure 18: Syntax of the "IM:message" trigger



 13.2 Actions

 13.2.1 "IM:sendmsg" Action

    "IM:sendmsg" actions cause the user agent to send an outgoing instant
    message.  Their syntax is shown in Figure 19.


          Node:  "IM:sendmsg"
       Outputs:  "accepted"     Next node if the message get accepted.
                 "failure"      Next node if failed to send the message.
                 "noanswer"     Next node if no response for the message
                                before timeout.
                 "redirection"  Next node if the message was redirected.
    Parameters:  "timeout"      Time to try before giving up sending message.

        Output:  "accepted"
    Parameters:  none

        Output:  "noanswer"
    Parameters:  none

        Output:  "failure"
    Parameters:  none

        Output:  "redirection"
    Parameters:  none


    Figure 19: Syntax of the "IM:sendmsg" node



    The parameters and outputs of "IM:sendmsg" actions are the same those
    for "call" actions, as defined in Section 5.4.5.

 13.3 IANA Considerations

    This extension registers a new URN per RFC 2141 [6], RFC 2648 [7],



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    and RFC 3688 [8].

    The XML namespace urn:ietf:params:xml:ns:less:im will only refer to
    the version of LESS mid-call handling extension in this document and
    will not change. Any other LESS enhancements MUST be made by
    extensions and MUST have different namespaces.

 13.3.1 URN Sub-Namespace Registration for urn:ietf:params:xml:ns:less:im

         URI: urn:ietf:params:xml:ns:less:im

         Registrant Contact: Xiaotao Wu <xiaotaow@cs.columbia.edu
              Henning Schulzrinne <hgs@cs.columbia.edu

         XML:

               BEGIN
               <?xml version="1.0"?
               <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
                   "http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd"
               <html xmlns="http://www.w3.org/1999/xhtml"
               <head
                 <meta http-equiv="content-type"
                    content="text/html;charset=iso-8859-1"/
                 <titleInstant Messaging Extension of the Language for End System Services Namespace</title
               </head
               <body
                 <h1Namespace for the Instant Messaging Extension of the Language for End System Services</h1
                 <h2urn:ietf:params:xml:ns:less:im</h2
                 <p<a href="[[[URL of published RFC]]]"RFCXXXX</a.</p
               </body
               </html
               END


 13.3.2 Schema registration

    This specification registers XML Schema for LESS, as per the
    guidelines in [8].

         URI: urn:ietf:params:xml:schema:less:im

         Registrant contact:
              Xiaotao Wu <xiaotaow@cs.columbia.edu
              Henning Schulzrinne <hgs@cs.columbia.edu

         XML: The XML can be found in Section 19.2.




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 13.3.3 MIME Registration

    LESS Media extension has the same MIME type as LESS as defined in
    Section 8.3.

 14 Event Handling extension

    Event handling extension is used to handle event subscriptions and
    notifications. It has two triggers, one switch, and five actions
    defined.

 14.1 Triggers

 14.1.1 "Event:subscription" Trigger

    "Event:subscription" handles incoming event subscription.  Their
    syntax is shown in Figure 20.


                        Trigger:  "Event:subscription"
                     Parameters:  None


    Figure 20: Syntax of the "Event:subscription" trigger



 14.1.2 "Event:notification" Trigger

    "Event:notification" handles incoming event notification.  Their
    syntax is shown in Figure 21.


                        Trigger:  "Event:notification"
                     Parameters:  None


    Figure 21: Syntax of the "Event:notification" trigger



 14.2 Switches

 14.2.1 "Event:event-switch" Switch

    Event-switches allow a LESS script to make decisions based on the
    event values in an incoming event subscription or notification.  The
    syntax of "event-switch" is summarized in Figure 22.



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          Node:  "Event:event-switch"
       Outputs:  "event"               Specific event to match
    Parameters:  None

        Output:  "event"
    Parameters:  "package"             Match against a list of event packages.
                 "is"                  Match against an event list.


    Figure 22: Syntax of the "Event:event-switch" node



    The "event" output takes two parameters, "package" checks whether an
    event has a specific package name, "is" checks whether an event is
    one of the event specified in the event list.

 14.3 Actions

 14.3.1 "Event:approve" Action

    "Event:approve" actions cause the presence agent to approve an
    incoming event subscription.  Their syntax is shown in Figure 23.


          Node:  "Event:approve"
       Outputs:  None
     Next node:  None
    Parameters:  "expires"        Expiration duration for the subscription.



    Figure 23: Syntax of the "Event:approve" node



 14.3.2 "Event:deny" Action

    "Event:deny" actions cause the presence agent to deny an incoming
    event subscription.  Their syntax is shown in Figure 24.










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                               Node:  "Event:deny"
                            Outputs:  None
                          Next node:  None
                         Parameters:  None



    Figure 24: Syntax of the "Event:deny" node



    There are no parameters and outputs for the "Event:deny" action.

 14.3.3 "Event:defer" Action

    "Event:defer" actions cause the presence agent to defer the decision
    on an incoming event subscription. This will cause the event
    subscription in pending state.  Their syntax is shown in Figure 25.


                              Node:  "Event:defer"
                           Outputs:  None
                         Next node:  None
                        Parameters:  None



    Figure 25: Syntax of the "Event:defer" node



    There are no parameters and outputs for the "Event:defer" action.

 14.3.4 "Event:subscribe" Action

    "Event:subscribe" actions cause the presence agent to send an event
    subscription to a presentity.  Their syntax is shown in Figure 26.













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          Node:  "Event:subscribe"
       Outputs:  "approved"         Next node if the subscription was approved.
                 "denied"           Next node if the subscription was denied.
                 "pending"          Next node if the subscription was pending.
                 "noanswer"         Next node if the subscription was not
                                    answered before timeout.
                 "failure"          Next node if the subscription failed for
                                    any other reasons.
                 "redirection"      Next node if the subscription was redirected.
    Parameters:  "timeout"          Time to try before giving up the subscription.
                 "expires"          The duration of the subscription.
                 "package"          The event package to subscribe to.
                 "content"          The content (e.g., event filtering) in subscription.

        Output:  "approved"
    Parameters:  none

        Output:  "denied"
    Parameters:  none

        Output:  "pending"
    Parameters:  none

        Output:  "noanswer"
    Parameters:  none

        Output:  "failure"
    Parameters:  none

        Output:  "redirection"
    Parameters:  none


    Figure 26: Syntax of the "Event:subscribe" node



 14.3.5 "Event:notify" Action

    "Event:notify" actions cause the presence agent to send an event
    subscription to a presentity.  Their syntax is shown in Figure 27.









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          Node:  "Event:notify"
       Outputs:  "accepted"      Next node if the notification was accepted.
                 "noanswer"      Next node if the notification was not
                                 confirmed before timeout.
                 "failure"       Next node if the notification failed for
                                 any other reasons.
                 "redirection"   Next node if the notification was redirected.
    Parameters:  "timeout"       Time to try before giving up the notification.
                 "package"       The event package in notification.
                 "event"         The event in notification.
                 "##any"         Any other parameters for an event.

        Output:  "accepted"
    Parameters:  none

        Output:  "noanswer"
    Parameters:  none

        Output:  "failure"
    Parameters:  none

        Output:  "redirection"
    Parameters:  none


    Figure 27: Syntax of the "Event:notify" node



 14.4 IANA Considerations

    This extension registers a new URN per RFC 2141 [6], RFC 2648 [7],
    and RFC 3688 [8].

    The XML namespace urn:ietf:params:xml:ns:less:event will only refer
    to the version of LESS mid-call handling extension in this document
    and will not change. Any other LESS enhancements MUST be made by
    extensions and MUST have different namespaces.

 14.4.1 URN Sub-Namespace Registration for
    urn:ietf:params:xml:ns:less:event

         URI: urn:ietf:params:xml:ns:less:event

         Registrant Contact: Xiaotao Wu <xiaotaow@cs.columbia.edu
              Henning Schulzrinne <hgs@cs.columbia.edu




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         XML:

               BEGIN
               <?xml version="1.0"?
               <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
                   "http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd"
               <html xmlns="http://www.w3.org/1999/xhtml"
               <head
                 <meta http-equiv="content-type"
                    content="text/html;charset=iso-8859-1"/
                 <titleEvent Handling Extension of the Language for End System Services Namespace</title
               </head
               <body
                 <h1Namespace for the Event Handling Extension of the Language for End System Services</h1
                 <h2urn:ietf:params:xml:ns:less:event</h2
                 <p<a href="[[[URL of published RFC]]]"RFCXXXX</a.</p
               </body
               </html
               END


 14.4.2 Schema registration

    This specification registers XML Schema for LESS, as per the
    guidelines in [8].

         URI: urn:ietf:params:xml:schema:less:event

         Registrant contact:
              Xiaotao Wu <xiaotaow@cs.columbia.edu
              Henning Schulzrinne <hgs@cs.columbia.edu

         XML: The XML can be found in Section 19.2.

 14.4.3 MIME Registration

    LESS Media extension has the same MIME type as LESS as defined in
    Section 8.3.

 15 Location-based service extension

    This extension introduces two new switch nodes named where-switch and
    where-relation-switch.  The new switch nodes check people's physical
    locations and based on the location information to make call control
    decisions.

 15.1 Switches




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 15.1.1 "Location:where-switch" Switch

    "Where-switches" allow a LESS script to make call decisions based on
    the physical location information. They are summarized in Figure 28.















































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          Node:  "Location:where-switch"
       Outputs:  "where"                  Specific the location to match
    Parameters:  "type"                   "geospatial", "civil"
                 "uri"                    the location occupier's uri. If omited,
                                          check the script owner's location.

        Output:  "where"
    Parameters:  "longitude"              Longitude coordinates,
                                          valid only for geospatial type
                 "latitude"               Latitude coordinates,
                                          valid only for geospatial type
                 "altitude"               Altitude coordinates,
                                          valid only for geospatial type
                 "country"                Country of the location,
                                          valid only for civil type
                 "A1"                     National subdivisions
                                          (state, region, province, prefecture),
                                          valid only for civil type
                 "A2"                     County, parish, gun (JP), district (IN),
                                          valid only for civil type
                 "A3"                     City, township, shi (JP),
                                          valid only for civil type
                 "A4"                     City division, borough, city district, ward,
                                          chou (JP), valid only for civil type
                 "A5"                     neighborhood, block,
                                          valid only for civil type
                 "A6"                     street, valid only for civil type
                 "PRD"                    Leading street direction,
                                          valid only for civil type
                 "POD"                    Trailing street suffix,
                                          valid only for civil type
                 "STS"                    Street suffix, valid only for civil type
                 "HNO"                    House number, numeric part only,
                                          valid only for civil type
                 "HNS"                    House number suffix,
                                          valid only for civil type
                 "LMK"                    Landmark or vanity address,
                                          valid only for civil type
                 "LOC"                    Additional location information, such as room
                                          valid only for civil type
                 "FLR"                    Floor, valid only for civil type
                 "NAM"                    Name (residence, business or office occupant)
                                          valid only for civil type
                 "PC"                     Postal code, valid only for civil type
                 "distance"               Distance value to a specified location.
                                          Valid only if geospatial or
                                          civil location presented.



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                 "condition"              Valid only if distance presented.
                                          Value is (in|out|at|). Default value is "at".
                 "unit"                   Valid only if distance presented.
                                          Value is (m|km|mi|in|ft|yd|naut mi).
                                          Default value is "m".
                 "direction"              Direction relative to a specified location,
                                          Valid only if geospatial or
                                          civil location presented. Value is

 "(south|north|west|east|above|below)".


    Figure 28: Syntax of the "Location:where-switch" node



    Location:where-switches have two node parameters: The mandatory
    parameter "type" specifies the location type to match: either
    geospatial location, or civil location. The optional parameter "uri"
    specifies the location occupier's uri. If not provided, the location
    occupier will be the script owner.

    The "where" output tag may have one or more parameters, indicating
    the exact location to match.

    The "longitude", "latitude", and "altitude" are used to specify a
    geographical location. The country, "A1", "A2", "A3", "A4", "A5",
    "A6", "PRD", "POD", "STS", "HNO", "HNS", "LMK", "LOC", "FLR", "NAM",
    and "PC" are used to specify a civil location.

    The "distance" parameter cannot be used without geographical location
    or civil location specified. Usually, the distance parameter is used
    with geographical location since it is difficult to measure the
    distance to a civil location. The "condition" and "unit" parameters
    are used to provide more convenient ways for distance specification.
    The available unit values are (m|km|mi|in|ft|yd|naut mi), mapped to
    meter, kilometer, mile, inch, foot, yard, and nautical mile,
    accordingly.

    The "direction" parameter cannot be used without geographical
    location or civil location specified. The value "south" or "north"
    are usually used when latitude specified. The value "east" or "west"
    are usually used when longitude specified. The value "above" and
    "below" are usually used when altitude specified, or FLR specified.

 15.1.2 "Location:where-relation-switch"

    Location:where-relation-switches allow a LESS script to make call
    decisions based on the location relation of two persons. They are



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    summarized in Figure 29.


          Node:  "Location:where-relation-switch"
       Outputs:  "where-relation"                  Specific location relation to match
    Parameters:  "uri1"                            the first location occupier's uri
                 "uri2"                            the second location occupier's uri

        Output:  "where-relation"
    Parameters:  "distance"                        Distance value between two persons.
                 "condition"                       Valid only if distance presented.
                                                   Value is (in|out|at|).
                                                   Default value is "at".
                 "unit"                            Valid only if distance presented.
                                                   Value is (m|km|mi|in|ft|yd
                                                   |naut mi). Default value is "m".
                 "direction"                       Direction relation between two
                                                   persons, value is "(south|north|
                                                   west|east|above|below)".
                 "same"                            A space separated list containing
                                                   location attributes, e.g., LOC, that
                                                   two persons have the same value.
                 "difference"                      A space separated list containing
                                                   location attributes, that two
                                                   persons have different values.


    Figure 29: Syntax of the "Location:where-relation-switch" node



    Location:where-relation-switches have two node parameters:  The
    mandatory parameter "uri1" specifies the first location occupier's
    uri.  The optional parameter "uri2" specifies the second location
    occupier's uri. If not provided, the second location occupier will be
    the script owner.

    The "where-relation" output tag may have one or more parameters,
    indicating the exact relation to match.

    The "distance" parameter indicates the distance between two persons.
    The "condition" and "unit" parameters are used for distance
    measuring.  They have the same meanings as those defined in "where-
    switch".

    The "direction" parameter indicates relative positions between two
    persons. For example, "south" means uri1 is south of uri2.




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    The "same" and "difference" indicating the relationship between two
    persons' location attributes. The attributes can be geospatial
    location attributes, such as "longitude", "latitude", and "altitude".
    They can also be civil location attributes, such as country, "A1",
    "A2", "A3", "A4", "A5", "A6", "PRD", "POD", "STS", "HNO", "HNS",
    "LMK", "LOC", "FLR", "NAM", and "PC".

 15.2 IANA Considerations

    This extension registers a new URN per RFC 2141 [6], RFC 2648 [7],
    and RFC 3688 [8].

    The XML namespace urn:ietf:params:xml:ns:less:location will only
    refer to the version of LESS mid-call handling extension in this
    document and will not change. Any other LESS enhancements MUST be
    made by extensions and MUST have different namespaces.

 15.2.1 URN Sub-Namespace Registration for
    urn:ietf:params:xml:ns:less:location

         URI: urn:ietf:params:xml:ns:less:location

         Registrant Contact: Xiaotao Wu <xiaotaow@cs.columbia.edu
              Henning Schulzrinne <hgs@cs.columbia.edu

         XML:

               BEGIN
               <?xml version="1.0"?
               <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
                   "http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd"
               <html xmlns="http://www.w3.org/1999/xhtml"
               <head
                 <meta http-equiv="content-type"
                    content="text/html;charset=iso-8859-1"/
                 <titleLocation-based Service Extension of the Language for End System Services Namespace</title
               </head
               <body
                 <h1Namespace for the Location-based Service Extension of the Language for End System Services</h1
                 <h2urn:ietf:params:xml:ns:less:location</h2
                 <p<a href="[[[URL of published RFC]]]"RFCXXXX</a.</p
               </body
               </html
               END


 15.2.2 Schema registration




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    This specification registers XML Schema for LESS, as per the
    guidelines in [8].

         URI: urn:ietf:params:xml:schema:less:location

         Registrant contact:
              Xiaotao Wu <xiaotaow@cs.columbia.edu
              Henning Schulzrinne <hgs@cs.columbia.edu

         XML: The XML can be found in Section 19.2.

 15.2.3 MIME Registration

    LESS Media extension has the same MIME type as LESS as defined in
    Section 8.3.

 16 Queue handling extension

    Many call center services require queueing incoming calls for
    available operators. This extension defines two actions for queue
    operation.

 16.1 Actions

 16.1.1 "Queue:enqueue" Action

    "Queue:enqueue" actions cause the user agent to put an incoming call
    in a waiting queue.  Their syntax is shown in Figure 30.


          Node:  "Queue:enqueue"
       Outputs:  "full"           If the number of calls exceeds the "maxlen".
    Parameters:  "queue"          The name of the queue. Possible values can be
                                  any string. Two pre-defined names are "hold"
                                  and "callback", which hosts holding calls and
                                  calls waiting for callback, accordingly.
                                  If not provided, use user agent's default queue.
                 "maxlen"         The maximum calls can be held in the queue.

        Output:  "full"
    Parameters:  none


    Figure 30: Syntax of the "Queue:enqueue" node



 16.1.2 "Queue:dequeue" Action



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    "Queue:dequeue" actions cause the user agent to retrieve a call from
    a waiting queue.  Their syntax is shown in Figure 31.


          Node:  "Queue:dequeue"
       Outputs:  "success"        A call get retrieved.
                 "failure"        Queue empty or other reasons. "dequeue" failed.
    Parameters:  "queue"          The name of the queue. Possible values can be
                                  any string. Two pre-defined names are "hold"
                                  and "callback", which hosts holding calls and
                                  calls waiting for callback, accordingly.
                                  If not provided, use user agent's default queue.

        Output:  "success"
    Parameters:  none

        Output:  "failure"
    Parameters:  none


    Figure 31: Syntax of the "Queue:dequeue" node



 17 Examples

    The following sections investigate services suitable for end systems.
    We looked into ITU Q.1211 [16] services, AT&T 5ESS switch services
    [17], services defined in CSTA Phase III [18], and new services
    incorporated with other Internet services, such as email and presence
    information, for appropriate end system services.

 17.1 Q.1211 services

    The technical report by Lennox et al [19] illustrated how to use SIP
    to handle Q.1211 services.  In table 1 of that report, it defines
    what Q.1211 services are suitable for end systems. We only focuses on
    the services appropriate for end systems and tries to use LESS to
    program those services.

 17.1.1 Abbreviated dialing (ABD)

    "Abbreviated dialing allows the definition of short (e.g., two digit)
    digit sequences to represent the actual dialing digit sequence for a
    public or private numbering scheme."

    Internet telephony end systems may simply use speed-dial buttons to
    handle the work. Instead of dialing a digit sequence, a single



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    button-click may trigger a call. End systems may also use LESS
    service scripts to do the translation from a short sequence to an
    actual sequence. Below is a LESS script example for the ABD service.


    <less
      <UI:command command="call"
        <address-switch field="destination"
          <address is="tel:11; phone-context=local"
            <location url="tel:+1-212-939-7054"
              <call/
            </location
          </address
        </address-switch
      </UI:command
    </less



 17.1.2 Attendant (ATT)

    "This allows VPN users to access an attendant (operator) position
    within the VPN for providing VPN service information (e.g., VPN
    numbers) by dialing a special access code. An Internet telephony end
    system needs only to be configured with an address of an appropriate
    local operator to translate the special access code to the actual
    local address of an attendant, or some address which will resolve to
    that address."  For LESS, this is similar to the ABD service (Section
    17.1.1) handling.

 17.1.3 Authentication (AUTC)

    "This allows verification that a user is allowed to access certain
    options in the telephone network. This should be in basic end system
    implementation."


    <less
      <UI:command command="call"
        <authenticate user="{message.origin}" target="local"
          <success
            <!-- If authentication succeeded, accept the call --
            <call/
          </success
          <failure
            <!-- If authentication failed, terminate the call attempt--
            <terminate/
          </failure



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        </authenticate
      </UI:command
    </less



 17.1.4 Authorization code (AUTZ)

    "This allows a user (typically in a VPN) to override the restrictions
    placed on the system from which calls are made. This should be in
    basic end system implementation."  Though we can user LESS scripts to
    automate the authorization process, it is unsafe to save the codes in
    LESS scripts.

 17.1.5 Automatic call back (ACB)

    "This feature allows the called party to automatically call back the
    calling party of the last call directed to the called party."

    This can be handled by either end systems or network servers. If
    handled by a network server, the network server should send a SIP
    REFER request to the calling party to initiate the call back (This is
    more like traditional Automatic Callback service).

    The service involves two steps, one is to log received invitations,
    the other is to retrieve the invitations and make calls.  Below is a
    LESS service script handling this service.


    <less
      <incoming
        <status-switch status-name="activity"
          <status is="busy"
            <reject
              <!-- Any action should have a 'next' for subsequent actions --
              <!-- If one action has a sibling action, the sibling action
                   will be executed in parallel with this action --
              <next
                <!-- A "callback" queue is defined --
                <Queue:enqueue queue="callback"/
              </next
            </reject
          </status
        </status-switch
      </incoming
      <Event:notification
        <address-switch field="origin"
          <address url="{agent.uri}"



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            <Event:event-switch
              <Event:event package="presence" status="open" activity=""
                <!-- If no 'number' parameter provided, the Queue:dequeue action
                     will sequentially retrieve all elements in the queue --
                <Queue:dequeue queue="callback"
                  <success
                    <call/
                  </success
                </Queue:dequeue
              </Event:event
            </Event:event-switch
          </address
        </address-switch
      </Event:notification
    </less



 17.1.6 Call distribution (CD)

    "This service feature allows the served user to specify the
    percentage of calls to be distributed among two or more destinations.
    Other criteria may also apply to the distribution of calls to each
    destination."

    This is usually done by network servers. If we extend CPL with a
    switch checking multiple destinations' status, we can handle the
    service in a proxy server by using CPL.

 17.1.7 Call forwarding (CF)

    "This service feature allows a user to have his incoming calls
    addressed to another number, no matter what the called party line
    status may be."  A simple LESS script can handle this below:


    <less
      <incoming
        <location url="sip:bob-home@example.com"
          <redirect/
        </location
      </incoming
    </less



 17.1.8 Call forwarding on busy/don't answer (CFC)




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    "This service feature allows the called user to forward particular
    calls if the called user is busy or does not answer within a
    specified number of rings."

    This service requires an end system to check its status and make call
    decisions. The following script forwards calls on busy.


    <less
      <incoming
        <status-switch status-name="activity"
          <status is="on-the-phone"
            <location url="sip:bob-home@example.com"
              <redirect/
            </location
          </status
        </status-switch
      </incoming
    </less



    The following script is for call forwarding on no answer.


    <less
      <incoming
        <alert timeout="2000"
          <timeout
            <location url="sip:bob-home@example.com"
              <redirect/
            </location
          </timeout
        </alert
      </incoming
    </less



 17.1.9 Call gapping (GAP)

    "This feature allows the service provider to restrict the number of
    calls to a served user to prevent congestion of the network."  This
    service should be implemented in network servers. A similar feature,
    Call Limiter (LIM) (Section 17.1.11), will do the similar thing but
    for end systems.

 17.1.10 Call hold with announcement (CHA)



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    "The call hold with announcement service feature allows a subscriber
    to place a call on hold with options to play music or customized
    announcements to the held party."  This service requires user
    interaction. A LESS script that can enhance the service by
    customizing the announcements based on addresses is shown below:


    <less
      <!-- A trigger to handle user input --
      <!-- For portability, the values for the parameter 'command'
           are pre-defined, each command can only be applied under a
           certain condition. 'hold' can only be used with an
           ongoing call --
      <UI:command command="hold"
        <address-switch field="destination"
          <address is="sip:bob@example.com"
            <Media:media media="audio" input="music.au" mode="sendonly"
              <Media:mediaupdate/
            </Media:media
          </address
        </address-switch
      </UI:command
    </less



 17.1.11 Call limiter (LIM)

    "This service feature allows a served user to specify the maximum
    number of simultaneous calls to a served user's destination. If the
    destination is busy, the call may be routed to an alternative
    destination."

    Internet telephony end systems can have virtually unlimited lines.
    However, the resources (CPU, memory, I/O devices) are limited for an
    end device so the number of simultaneous calls is limited. This can
    be handled by a LESS script below:


    <less
      <incoming
        <status-switch status-name="active-calls"
          <status equal="2"
            <reject status="busy"/
          </status
        </status-switch
      </incoming
    </less



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 17.1.12 Call logging (LOG)

    "This service feature allows for a record to be prepared each time
    that a call is received to a specified telephone number."  The <log
    action in LESS can handle this feature.


    <less
      <incoming
        <log/
      </incoming
    </less



 17.1.13 Call queueing (QUE)

    "This service feature allows calls which would otherwise be declared
    busy to be placed in a queue and connected as soon as the free
    condition is detected. Upon entering the queue, the caller hears an
    initial announcement informing the caller the call will be answered
    when a line is available."

    The call queueing service can be handled by an application server in
    the network. End systems can also handle it. The LESS script below
    handles the service.


    <less
      <incoming
        <status-switch status-name="active-calls"
          <!-- For more than one active call, we use 'active-calls="1+" --
          <status equal="1"
            <Media:media media="audio" input="music.au" mode="sendonly"
              <accept
                <next
                  <Queue:enqueue queue="hold"/
                </next
              </accept
            </Media:media
          </status
        </status-switch
      </incoming
      <Event:notification
        <status-switch status-name="active-calls"
          <status equal="0"
            <!-- Retrieve only one call from the hold queue --
            <Queue:dequeue queue="hold" number="1"



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              <success
                <Media:media media="audio" input="microphone" mode="sendrecv"
                  <Media:mediaupdate/
                </Media:media
              </success
            </Queue:dequeue
          </status
        </status-switch
      </Event:notification
    </less



 17.1.14 Call transfer (TRA)

    "The call transfer service feature allows a subscriber to place a
    call on hold and transfer the call to another location."

    In LESS, the <transfer action is used to handle the service.  Call
    transfer is a user triggered service. A LESS script can be triggered
    by a user input event to perform a transfer.


    <less
      <!-- the 'transfer' command only applies to the current ongoing call --
      <UI:command command="transfer"
        <!-- Transfer all calls between 09:00 ~ 17:00 to specialist@foo.com,
             otherwise, to technician@foo.com --
        <time-switch
          <time dtstart="20040716T090000Z"
            duration="PT8H" freq="weekly" byday="MO,TU,WE,TH,FR"
            <location uri="specialist@foo.com"
              <transfer/
            </location
          </time
          <otherwise
            <location uri="technician@foo.com"
              <transfer/
            </location
          </otherwise
        </time-switch
      </UI:command
    </less



 17.1.15 Call waiting (CW)




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    "This service feature allows a subscriber to receive a notification
    that another party is trying to reach his number while he is busy
    talking to another calling party."

    Since an Internet telephony end system can have multiple lines and a
    better user interface, such as a bigger LCD display, it can alert
    users for any new calls. No service scripts required for this
    service.

 17.1.16 Closed user group (CUG)

    "This service feature allows the user to be a member of a set of
    users who are normally authorized to make and receive calls only
    within the group."

    This service should be put on network servers, though end systems can
    handle it by using call screening services. We will introduce call
    screening services in Section 17.1.30 and 17.1.37.

 17.1.17 Consultation calling (COC)

    "The consultation calling service feature allows a subscriber to
    place a call on hold, in order to initiate a new call for
    consultation."

    For Internet telephony end systems, this service is similar to Call
    hold with announcements (CHA), which we have discussed in Section
    17.1.10.

 17.1.18 Customer profile management (CPM)

    "This service feature allows the subscriber to real-time manage his
    service profile, i.e. terminating destinations, announcements to be
    played, call distribution, and so on."

    This is about service script management. There should be a friendly
    service creation and management user interface for end systems.

 17.1.19 Customer recorded announcement (CRA)

    "This service allows a call to be completed to a (customized)
    terminating announcement instead of a subscriber line.  The served
    user may define different announcements for unsuccessful call
    completions due to different reasons (e.g. caller outside business
    hours, all lines are busy)."  The switches in LESS can do the
    customization work.  For example, a time-based customization is as
    below:




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    <less
      <incoming
        <!-- Effective from 07/16/2004, if an incoming call is after
             05:00:00 PM Friday, and before 09:00:00 AM Monday, play
             the no_office_hour.au announcement --
        <time-switch
          <time dtstart="20040716T170000Z"
            duration="PT16H" freq="weekly" byday="MO,TU,WE,TH,FR"
            <Media:media media="audio" source="no_office_hour.au" mode="sendonly"
              <accept/
            </Media:media
          </time
        </time-switch
      </incoming
    </less



 17.1.20 Customized ringing (CRG)

    "This service feature allows the subscriber to allocate a distinctive
    ringing to a list of calling parties."

    This service can only be handled in an end system. The script below
    shows an enhanced version not only based on address but also based on
    priority of the call to perform customized ringing.


    <less
      <incoming
        <priority-switch
          <priority equal="emergency"
            <alert priority="emergency"/
          </priority
          <otherwise
            <address-switch field="origin"
              <address is="sip:bob@example.com"
                <alert audio="bob.au"/
              </address
              <otherwise
                <alert/
              </otherwise
            </address-switch
          </otherwise
        </priority-switch
      </incoming
    </less




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 17.1.21 Destination user prompter (DUP)

    "This service feature enables to prompt the called party with a
    specific announcement. Such an announcement may ask the called party
    enter an extra numbering, e.g. through DTMF, or a voice instruction
    that can be used by the service logic to continue to process the
    call."


         Though we can use LESS <Media:media modifier to easily
         play an announcement, it is out of LESS's scope to handle
         DTMF inputs. The DTMF handling falls into VoiceXML's [20]
         domain.  For example, UI:prompt script="input1.vxml"/.
         More investigation is required on integrating VoiceXML into
         LESS.

 17.1.22 Follow-me diversion (FMD)

    "With this service feature, a user may register for incoming calls to
    any terminal access." This service should be in network servers.

 17.1.23 Mass calling (MAS)

    "This service feature allows processing of huge numbers of incoming
    calls, generated by broadcasted advertisings or games." This service
    should be handled by network servers.

 17.1.24 Meet-me conference (MMC)

    "This service feature allows the user to reserve a conference
    resource for making a multi-party call. At a specified date and time,
    each participant in the conference has to dial a designated number in
    order to have access to the conference."  This is a standard
    conferencing service.  We can use LESS to perform time and caller
    checking, and authentication.


    <less
      <incoming
        <time-switch
          <!-- a conference on every Monday from 17:00 to 19:00 --
          <time dtstart="20040716T170000Z"
            duration="PT2H" freq="weekly" byday="MO"
            <address-switch field="origin"
              <address is="sip:bob@example.com"
                <authenticate user="{message.destination}" target="remote"
                  <success
                    <accept/



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                  </success
                </authenticate
              </address
            </address-switch
          </time
      </incoming
    </less



 17.1.25 Multi-way calling (MWC)

    "This service feature allows the user to establish multiple,
    simultaneous telephone calls with other parties."

    An Internet telephony end system can initiate as many simultaneous
    calls as it wishes as long as the network bandwidth and the CPU
    processing speed permit. A changed version of the service will be to
    put a limit on the number of simultaneous calls. The changed version
    can be handled by a LESS script below:


    <less
      <UI:command command="call"
        <status-switch status-name="active-calls"
          <status equal="2"
            <terminate
              <next
                <alert message="Only 2 active calls allowed"/
              </next
            </terminate
          </status
        </status-switch
      </UI:command
    </less



 17.1.26 Off-net access (OFA)

    "This service feature allows a VPN user to access his or her VPN from
    any non-VPN station in the PSTN by using a personal identification
    number (PIN)."  This service should not be handled by using LESS
    scripts.

 17.1.27 Off-net calling (ONC)

    "This service feature allows the user to call outside the VPN



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    network."

    This service is just a standard firewall traversal process, no
    service scripts required.

 17.1.28 One number (ONE)

    "This feature allows a subscriber with two or more terminating lines
    in any number of locations to have a single telephone number. This
    allows businesses to advertise just one telephone number throughout
    their market area and to maintain their operations in different
    locations to maximize efficiency. The subscriber can specify which
    calls are to be terminated on which terminating lines based on the
    area the calls originate."

    This is a standard SIP proxy service, not handled by end systems.

 17.1.29 Origin dependent routing (ODR)

    "This service feature enables the subscriber to accept or reject a
    call, and in case of acceptance, to route this call, according to the
    calling party geographical location. This service feature allows the
    served user to specify the destination installations according to the
    geographical area from which the call was originated."

    This service requires <Location:where-switch to handle location-
    based call routing. A service script below can handle the service.
    For end systems, we use <redirect/ action to route calls. A proxy
    server is a more appropriate place to host the service, and use
    <proxy/ action to route calls.


    <less
      <incoming
        <address-switch field="origin"
          <address is="sip:bob@example.com"
            <Location:where-switch type="civil" principle="sip:bob@example.com"
              <Location:where country="USA" A1="New York"
                A3="New York" A6="West 120th" HNO="450" LOC="Room 563"
                <location url="sip:bob-office@example.com"
                  <redirect/
                </location
              </Location:where
              <otherwise
                <location url="sip:bob-mobile@example.com"
                  <redirect/
                </location
              </otherwise



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            </Location:where-switch
          </address
        </address-switch
      </incoming
    </less



 17.1.30 Originating call screening (OCS)

    "This service feature allows the served user to bar calls from
    certain areas based on the District code of the area from which the
    call is originated."  This service can be handled by using address-
    switch.


    <less
      <incoming
        <address-switch field="destination" subfield="host"
          <address is="example.com"
            <reject status="reject"/
          </address
        </address-switch
      </incoming
    </less



 17.1.31 Originating user prompter (OUP)

    "This service feature allows a served user to provide an announcement
    which will request the caller to enter a digit or series of digits
    via a DTMF phone or generator. The collected digits will provide
    additional information that can be used for direct routing or as a
    security check during call processing."

    This service can be in a network server or a user agent. To enable a
    user agent to support this service, it requires the user agent to
    handle the interaction with remote users.

 17.1.32 Personal numbering (PN)

    "This service feature supports a UPT number that uniquely identifies
    each UPT user and is used by the caller to reach that UPT user."
    Reaching a user through a personal address is accomplished simply by
    a proxy or redirection server which locates the user.

 17.1.33 Premium charging (PRMC)



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    "This service feature allows for the pay back of part of the cost of
    a call to the called party."  This service is out of the scope of
    LESS.

 17.1.34 Private numbering plan (PNP)

    "This service feature allows the subscriber to maintain a numbering
    plan within his private network, which is separate from the public
    numbering plan."  This service should usually be put in outbound
    proxy servers. If we provide such service in end systems, it would be
    similar to the Abbreviated dialing (ABD) service we introduced in
    Section 17.1.1.

 17.1.35 Reverse charging (REVC)

    "This service feature allows the service subscriber (e.g. freephone)
    to accept to receive calls at its expense and be charged for the
    entire cost of the call."

    This service and the next service "Split charging" require a detailed
    VoIP charging schema and have the charging information available to
    users. Currently, LESS cannot handle this kind of service.  However,
    if call signaling messages can provide charging information, LESS
    scripts can perform call decisions, such as automatically rejecting a
    reverse charging calls unless it is from certain users, based on the
    charging information.

 17.1.36 Split charging (SPLC)

    "This service feature allows for the separation of charges for a
    specific call, the calling and called party each being charged for
    one part of the call."  This service is similar to the previous
    service, LESS cannot handle the service.

 17.1.37 Terminating call screening (TCS)

    "This service feature allows the user to screen calls based on the
    terminating telephone number dialed."  Below is a LESS script example
    handling this service.


    <less
      <incoming
        <address-switch field="destination" subfield="host"
          <address is="example.com"
            <reject status="reject"/
          </address
        </address-switch



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      </incoming
    </less



 17.1.38 Time dependent routing (TDR)

    "This services feature allows the served user to apply different call
    treatments based on the time of day, day of week, day of year,
    holiday, etc."  Usually, routing services should be put in network
    servers, but we can perform similar services for time dependent
    redirecting. This can be handled by LESS time-switch.


    <less
      <incoming
        <time-switch
          <time dtstart="20040716T170000Z"
            duration="PT8H" freq="weekly" byday="MO"
            <location url="sip:bob@voicemail.com
              <redirect/
            </location
          </time
        </time-switch
      </incoming
    </less



 17.2 5ESS services

    In this section, we investigate the services introduced in "AT&T 5ESS
    Switch The Premier Solution, Feature Handbook" [17].  5ESS services
    including the following categories: BRCS (Business and Residence
    Custom Services) features, ISDN features (message and MBKS), Public
    Service features (emergency), Defense Switched Network Features, Toll
    and Tandem features, Interoffice Signaling and Control features,
    Operator Service Position System features, OA&M features. Among these
    categories, we are most interested in the BRCS features because many
    of BRCS features can be handled in end systems. For ISDN features, we
    will discuss the Message Services and the MBKS (Multibutton Key
    Telephone System).  For Public Service features, we will discuss the
    group alerting service.  We will not discuss the other service
    categories. We only list the services suitable for end systems.

 17.2.1 Attendant call transfer (also known as Call splitting)

    "The service allows the attendant to flash and dial a code before



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    dialing the third leg of a 3-way call. This inhibits the automatic
    connecting of all the parties to allow private consultation between
    the attendant and the third leg of the call. If the code is not
    dialed, the automatic 3-way is formed."

    Since an Internet telephony end system usually can have multiple
    lines, it is easy to put one line on hold and initiate another call.
    However, to enable this service, an end system should be able to
    merge an active call and a held call into a 3-way call.

    This service is not a programmable service, a user will manually use
    a second line to initiate the second call, and manually instruct his
    user agent to merge two calls.

 17.2.2 Attendant camp-on

    "This service allows incoming calls that the attendant attempts to
    complete to a busy station to be held waiting until the busy station
    becomes idle. The busy station receives a tone (indication of camp-
    on) each time the attendant attempts a completion. The call being
    transferred receives audible ringing, special tone followed by
    audible ringing, or optional silence, while waiting for the busy
    station to answer the call."  The following script can handle the
    service.


    <less
      <incoming
        <status-switch status-name="active-calls"
          <!-- We use 1+ to represent 1 or more active-calls --
          <status greater="1"
            <Media:media source="wait.au" mode="sendonly"
              <accept
                <next
                  <Queue:enqueue queue="hold"/
                </next
              </accept
            </Media:media
          </status
        </status-switch
      </incoming
      <Event:notification
        <status-switch status-name="active-calls"
          <status is="0"
            <Queue:dequeue queue="hold" number="1"
              <success
                <Media:media media="audio" input="microphone" mode="sendrecv"
                  <Media:mediaupdate/



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                </Media:media
              </success
            </Queue:dequeue
          </status
        </status-switch
      </Event:notification
    </less



 17.2.3 Attendant conference

    "This service enables an attendant to initiate a conference call
    involving up to six parties (including attendant). The selection of a
    special conference attendant can be done from any station within the
    same customer group by dialing a particular access code."

    There are two ways to handle conferencing services in an end system,
    one is to have all conference participants to connect to a conference
    server (by REFER or third-party call control), the other is to use
    end system mixing. The first way is more scalable, but requires an
    external conference server. The second way requires an end system
    supporting mixing. The following scripts show both ways for a time-
    based conference initiation.


    <less
      <!-- Use SIP REFER --
      <timer dtstart="20040716T170000Z"
        duration="PT2H" freq="weekly" byday="MO"
        <lookup source="sip:bob@example.com
                sip:tom@example.com sip:alice@abc.com"
          <success
            <call
              <success
                <location url="sip:conf@example.com"
                  <transfer/
                </location
              </success
            </call
          </success
        </lookup
      </timer
    </less



    The script will automatically send a call invitation to each URL in



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    the list, once a call established, the script will transfer the call
    to the conference server at sip:conf@example.com.


    <less
      <!-- Use local mixing --
      <timer dtstart="20040716T170000Z"
        duration="PT2H" freq="weekly" byday="MO"
        <sub ref="IRTdef"/
        <lookup source="sip:bob@ex.com sip:tom@ex.com"
          <success
            <call subject="Group meeting"
              <success
                <merge subject="Group meeting"/
              </success
            </call
          </success
        </lookup
      </timer
    </less



 17.2.4 Authorization code

    "The codes allow the station user to input an assigned code to change
    the restrictions associated with the originating station to those
    associated with the assigned authorization code. Thus, unauthorized
    use of facilities is avoid."


    <less
      <UI:command command="call"
        <address-switch field="destination"
          <address is="sip:conf123@example.com"
            <call
              <success
                <IM:sendmsg type="dtmf" digits="123456"/
              </success
            </call
          </address
        </address-switch
      </UI:command
    </less



 17.2.5 Automatic recall



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    "This service lets the customer automatically call the LOCDN (last
    outgoing call directory number) currently associated with the
    customer's station when both stations become idle. It is different
    from Automaticall Callback, which automatically places a call on
    LICDN (last incoming call directory number)."  The service script
    below shows how to program the service in LESS.


    <less
      <UI:command command="call"
        <call
          <failed status="486,603"
            <Queue:enqueue queue="callback"
              <next
                <Event:subscribe/
              </next
            </Queue:enqueue
          </failed
        </call
      </UI:command
      <Event:notification
        <Event:event-switch
          <Event:event activity="normal"
            <!-- User {message.origin} to represent the sender of the notification--
            <Queue:dequeue queue="callback" match="{message.origin}"
              <success
                <call/
              </success
            </Queue:dequeue
          </Event:event
        </Event:event-switch
      </Event:notification
    </less



 17.2.6 Call forwarding busy line (CFBL)

    "This service permits calls attempting to terminate to a busy line to
    be redirected to another customer-specified line."  The following
    script can handle the service.


    <less
      <incoming
        <status-switch status-name="active-calls"
          <status greater="1"
            <location url="sip:phone2@example.com"



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              <redirect/
            </location
          </status
        </status-switch
      </incoming
    </less



 17.2.7 Call forwarding busy line--incoming only

    "This service provides that only incoming DID calls are forwarded to
    the specified business group line on busy. Intragroup call attempts
    and attempts from private facilities to terminate to the busy line
    receive busy treatment."  This is in fact address-based call
    forwarding services.


    <less
      <incoming
        <status-switch status-name="active-calls"
          <status greater="1"
            <address-switch field="origin"
              <address isnot="sip:*@example.com"
                <location url="sip:phone2@example.com"
                  <redirect/
                </location
              </address
            </address-switch
          </status
        </status-switch
      </incoming
    </less



 17.2.8 Call forwarding--don't answer

    "This service forwards incoming calls to a station when the called
    station is not answered after a customer-specified number of ringing
    cycles."  The script below can handle the service.


    <less
      <incoming
        <alert timeout="2000"
          <timeout
            <location url="sip:phone2@example.com"



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              <redirect/
            </location
          </timeout
        </alert
      </incoming
    </less



 17.2.9 Unconditional call forwarding

    "This service forwards all incoming calls to another telephone."  We
    can simply handle the service by using <redirect/ action.


    <less
      <incoming
        <location url="sip:bob@room123.example.com"
          <redirect/
        </location
      </incoming
    </less



 17.2.10 Call hold

    "This service allows a station user to 'hold' a call in progress by
    flashing and then dialing the call hold code. This frees the line for
    originating another call, answering a waiting call, or returning to a
    held call."  In LESS, we use the action <Media:mediaupdate/ to
    change the media source for "hold" and "unhold" service.


      ...
      <!-- hold --
      <Media:media media="audio" input="music.au" mode="sendonly"
        <Media:mediaupdate/
      </Media:media
      ...
      <!-- unhold --
      <Media:media media="audio" input="microphone" mode="sendrecv"
        <Media:mediaupdate/
      </Media:media



 17.2.11 Call transfer--individual--all calls



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    "This service allows a station user to transfer any established call
    to another station within or outside the PBX or business group
    without the assistance of the attendant. This is accomplished by
    flashing while on a stable 2-party call, dialing the desired party,
    and hanging up the telephone."  The <transfer/ action can handle
    this service.


    <less
      <incoming
        <media media="audio" input="transfer.au" mode="sendonly"
          <accept
            <next
              <location url="sip:bob@room123.example.com"
                <transfer
                  <failed
                    <media media="audio" input="failed.au" mode="sendonly"
                      <mediaupdate/
                    </media
                  </failed
                </transfer
              </location
            </next
          </accept
        </media
      </incoming
    </less



 17.2.12 Call waiting and cancel call waiting

    Since an Internet telephony end system usually have multiple lines,
    users do not have to use flash button to switch calls. However, users
    should be able to control how many active calls an end device can
    handle.  The following script can help to configure the maximum
    number of calls.


    <less
      <incoming
        <status-switch status-name="active-calls"
          <status greater="3"
            <reject reason="busy"/
          </status
        </status-switch
      </incoming
    </less



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 17.2.13 Circle hunting

    "This service allows all lines in a multiline hunt group to be tested
    for busy, regardless of the point of entry into the group. When a
    call is made to a line in an MLHG, a regular hunt is performed
    starting at the terminal associated with the dialed number. It
    continues to the last terminal in the MLHG, then proceeds to the
    first terminal in the group and continues to hunt sequentially
    through the remaining lines in the group. Busy tone is returnedif the
    called terminal is reached without finding one that is idle."  This
    service is more suitable for a proxy server to handle. However, we
    can also handle it in an end system by using <transfer/ action.


    <less
      <incoming
        <media type="audio" input="wait.au" mode="sendonly"
          <accept
            <next
              <lookup source="sip:bob@ex.com sip:tom@ex.com"
                      order="sequential"
                <success
                  <transfer
                    <succeed
                      <stop/
                    </succeed
                  </transfer
                </success
              </lookup
            </next
          </accept
        </media
      </incoming
    </less



 17.2.14 Conference calling

    "The service allows a station user to establish a conference call
    involving up to five other parties without attendant assistance."
    This service is almost the same as the attendant conferencing service
    we discussed before, it requires an end system to support mixing, and
    to merge an incoming call to an existing conference call. We use
    <merge/ action to handle the merge.

 17.2.15 Customer-changeable speed calling




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    "This service allows subscribers to assign their own Speed Calling
    codes directly and immediately from their own telephone by dialing a
    change Speed Calling list access code, an abbreviated code and a new
    telephone number. It is available for 1- and or 2-digit Speed Calling
    list owners."  In an end system, speed dialing modification should be
    done by editing service scripts from a local GUI. Below is a script
    for speed dialing handling.


    <less
      <UI:command command="call"
        <address-switch field="destination" subfield="user"
          <address is="1"
            <location url="sip:bob@example.com"
              <call/
            </location
          </address
        </address-switch
      </UI:command
    </less



 17.2.16 Direct connect

    "This service automatically places a call to a preselected called
    number when a station goes off-hook. This feature can be used for
    introffice and interoffice calls and does not affect termination to a
    line."  This service requires a specially configured UA. The service
    should not be handled by a service script.

 17.2.17 Distinctive ringing

    This service applies a distinctive ringing to determine the source of
    an incoming call. The following script handles the service.


    <less
      <incoming
        <address-switch field="origin"
          <address is="sip:bob@example.com"
            <alert audio="bob.au"/
          </address
        </address-switch
      </incoming
    </less





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 17.2.18 Four- and eight-party

    "This service provides POTS for up to four or eight customers sharing
    the same line. It provides fully selective ringing or semiselective
    ringing for up to four customers and semiselective ringing for five
    to eight customers."  The following script plays distinctive ringing
    for different user sharing the same phone.


    <less
      <incoming
        <address-switch field="destination"
          <address is="sip:bob@example.com"
            <alert audio="bob.au"/
          </address
          <otherwise
            <address-switch field="destination"
              <address is="sip:tom@example.com"
                <alert audio="tom.au"/
              </address
              <otherwise
                <address-switch field="destination"
                  <address is="sip:mary@example.com"
                    <alert audio="mary.au"/
                  </address
                </address-switch
              </otherwise
            </address-switch
          </otherwise
        </address-switch
      </incoming
    </less



 17.2.19 Recorded telephone dictation

    "This service permits access to and control of customer-owned
    dictating equipment from a station in the customer group."  This
    service requires an end system to be able to record and playback a
    phone call.


    <less
      <UI:command command="accept"
        <address-switch field="origin"
          <address is="sip:bob@example.com"
            <log record="true"/



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          </address
        </address-switch
      </UI:command
    </less



 17.2.20 Time-of-Day features

    "This kind of features can perform automatic actions based on time-
    of-day.  For example, Slumber Service (also known as Do Not Disturb)
    can temporarily prohibit an individual customer station or a
    functional group of individual stations from receiving calls. It is
    used in hospitals to restrict incoming calls to patients during the
    night or any designated period."  We can use LESS time-switch to
    handle the service.


    <less
      <incoming
        <time-switch
          <time dtstart="20040716T230000Z"
            duration="PT8H" freq="daily"
            <reject reason="Do not disturb"/
          </time
        </time-switch
      </incoming
    </less



 17.2.21 Message services

    ISDN Message Services provides centralized and personalized call
    coverage of message answering capabilities. For Basic Message
    Service, calls to a message service client are redirected via one of
    the following features.

         Call forward -- busy line

         Call forward -- don't answer

         Call forward -- variable
         To provide the personalized call coverage, message service
         attendants can be equipped with special ISDN station sets that
         display call information on calls directed to the message
         service center. The following information is available for
         display: Call type, Originating party DN, Calling party DN. This



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         service requires an end system can identify a message service,
         e.g., a voicemail server. The following script forward a call to
         a voicemail server when the user is busy.


    <less
      <incoming
        <status-switch status-name="active-calls"
          <status greater="2"
            <location url="sip:bob@voicemail.example.com"
              <redirect/
            </location
          </status
        </status-switch
      </incoming
    </less



    There can be additional features for message services, for example,
    message waiting indicator, which can inform a client that he/she has
    message(s) waiting. The Message Waiting Indication Event Package for
    SIP [21] can provide required message information. An end system
    should be able to handle the event for the message waiting indicator
    service.


    <less
      <Event:notification
        <Event:event-switch
          <Event:event package="message-summary" message-waiting="yes"
            <alert message="There are new messages for you" audio="mwi.au"/
          </Event:event
        </Event:event-switch
      </Event:notification
    </less



 17.2.22 Multibutton key telephone system (MBKS)

    "Feature Function Buttons on the MBKS set can be assigned to activate
    certain features. For example, a user can press the function button
    assigned to Automatic Callback on Busy when a busy number is dialed."
    We can bind a script to a specific button for this kind of services.

 17.2.23 Group alerting




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    "This service permits the controller (or alerting party), upon
    dialing a code, to signal a preselected number of telephones
    simultaneously. One-way communication is established from the
    controller to all members of the group that responded to the signal."
    The script below can handle the service.


    <less
      <UI:command command="call"
        <!-- define name="Alerting group"
             values="sip:security@abc.com sip:fire@abc.com" --
        <address-switch field="destination"
          <address is="sip:alert@example.com"
            <lookup source="sip:security@abc.com sip:fire@abc.com"
              <media mode="sendonly"
                <call subject="Alert"
                  <success
                    <merge subject="Alert"/
                  </success
                </call
              </media
            </lookup
          </address
        </address-switch
      </UI:command
    </less



 17.3 Services defined in CSTA Phase III

    In this section, we investigate the services in ECMA standard ECMA-
    269, "Services for Computer Supported Telecommunications Applications
    (CSTA) Phase III" [18]. The call model of CSTA services is to use
    protocol messages to control end systems. Many CSTA services are in
    fact simply actions in LESS. For example, Accept Call is a CSTA
    control service, but just an action, <accept/, in LESS.

    CSTA Phase III categorizes services into System Services, Monitoring
    Services, Snapshot Services, Call Control Services and Events, Call
    Associated Features, Media Attachment Services and Events, Routing
    Services, Physical Device Features, Logical Device Features, Device
    Maintenance Events, I/O Services, Data Collection Services, Voice
    Services and Events, and Call Detail Record (CDR) Services.  Among
    these services, System Services are used to handle the relationship
    between switch functions and CSTA service functions and are out of
    the scope of LESS, Monitoring Services are like to define the DPs
    (Detection Points) in Intelligent Network (IN) and are also out of



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    the scope of LESS. Snapshot Services are used to send device
    information to switch functions, not suitable for LESS. The Routing
    Services are not end system services and are also not suitable for
    LESS. The Device Maintenance Events, I/O Services, and Data
    Collection Services are too low-level for end user oriented service
    programming, thus they are not suitable for LESS. We will discuss the
    other services below.

 17.3.1 Accept call

    This service can be mapped to <alert/ action in LESS.

 17.3.2 Alternate call

    This service places an existing active call on hold and then retrieve
    a previously held call. This service in fact involves several
    actions. We can use the <Media:mediaupdate/ action to put a call
    held/unheld and put held calls into a queue by enqueue action.

 17.3.3 Answer call

    This service can be mapped to <accept/ action in LESS.

 17.3.4 Call back call-related

    The Call Back Call-Related service allows a computing function to
    request that the calling device retry the call to the called device
    when the called device is in an appropriate state to accept the call.
    This is the same as the ACB service described in Section 17.2.5.

 17.3.5 Call back message call-related

    The Call Back Message Call-Related service allows a computing
    function to request that the switching function leave a pre-defined
    message requesting that the called device call the calling device.
    For example, the called device may have been busy when called.


    <less
      <incoming
        <status-switch status-name="activity"
          <status is="on-the-phone"
            <alert message="Please call back {message.origin}"
              <next
                <Queue:enqueue queue="callback"/
              </next
            </alert
          </status



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        </status-switch
      </incoming
    </less



 17.3.6 Camp on call

    The Camp On Call service allows the computing function to queue a
    call for a device (that typically is busy) until that device becomes
    available.  The script below can handle the service.


    <less
      <incoming
        <status-switch status-name="active-name"
          <status greater="1"
            <media type="audio" input="wait.au" mode="sendonly"
              <accept
                <next
                  <Queue:enqueue queue="callback"/
                </next
              </accept
            </media
          </status
        </status-switch
      </incoming
    </less



 17.3.7 Clear call

    The Clear Call service releases all devices from an existing call.
    In the case of a conference call, this results in all devices in the
    conference call being released from the call. This service can be
    mapped to the <terminate/ action.

 17.3.8 Clear connection

    The Clear Connection service releases a specific device from a call.
    In the case of a two-party call, this may result in the call being
    torn down. In the case of a conference call, this results in the
    specific party being removed from the conference.  For a two-party
    call, it is the same as Clear Call and can be represented by the
    <terminate/ action. For a conference call, we need to provide a
    parameter to the <terminate/ action to indicate which call leg
    should be disconnected. We can use a SIP url to identify the call



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    leg.

 17.3.9 Conference call

    The Conference Call service provides a conference of an existing held
    call and another active call at a conferencing device. This is the
    same as the 3-way calling service. It requires LESS to have a
    <merge/ command to merge multiple two-party calls into a conference
    call.

 17.3.10 Consultation call

    The Consultation Call service places an existing active call at a
    device on hold and initiates a new call from the same device. This is
    in fact two actions in LESS, using <Media:mediaupdate/ to put a call
    on hold and using <call/ to initiate a new call.

 17.3.11 Deflect call

    The Deflect Call service allows the computing function to divert a
    call to another destination that may be inside or outside the
    switching sub-domain. This can be mapped to LESS <transfer/ action.

 17.3.12 Dial digits

    The Dial Digits service allows the computing function to perform a
    dialing sequence that is associated with a call that has already been
    initiated. This service is used to send message out after a call
    invitation and we use <IM:sendmsg to handle the action.

 17.3.13 Directed pickup call

    The Directed Pickup Call service moves a specified call and connects
    it at a new specified destination.  This results in the connection
    being diverted to a new destination inside the switching sub-domain.
    This service should not be handled by end systems, but by an
    application server in the network.

 17.3.14 Group pickup call

    The Group Pickup Call service moves a call that is a member of a
    specified or default pickup group to a new specified destination. The
    same as Directed Pickup Call, this service should be handled by an
    application server in the network.

 17.3.15 Hold call

    The Hold Call service places a connected connection on hold at the



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    same device.  The <Media:mediaupdate/ action in LESS handles this
    service and <enqueue action can put a call in a queue.

 17.3.16 Intrude call

    The Intrude Call service adds the calling device to a call at a busy
    called device. Depending upon the switching function, the result will
    be that the calling device is either actively or silently
    participating in the called device's existing call or consulting with
    the called device with a new call. This can be handled by LESS
    <merge/ action with the <media modifier set as mode="sendonly" for
    silently participating.

 17.3.17 Join call

    The Join Call service allows a computing function to request, on
    behalf of a device, that the device be joined into an existing call.
    This can also be handled by LESS <merge/ action.

 17.3.18 Make call

    The Make Call service allows the computing function to set up a call
    between a calling device and a called device. This can be handled by
    LESS <call/ action.

 17.3.19 Make predictive call

    The Make Predictive Call service shall originate a call between two
    devices by first creating a connection to the called device. The
    service returns a positive acknowledgement that provides the
    connection at the called device.  Subsequent actions are taken
    depending upon the call progress and the actions requested. This
    service makes additional actions based on the result of <call/
    action. For example,


    <less
      <UI:command command="call"
        <call
          <success
            ....
          </success
          <redirected
            ...
          </redirected
          <rejected
            ...
          </rejected



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        </call
      </UI:command
    </less



 17.3.20 Park call

    The Park Call service moves a specified call at a device to a
    specified (parked-to) destination. Two ways to handle this in an end
    system, the first is to transfer the call to a resource server, the
    second is to change the media input of the call as described in
    Section 17.1.10.

 17.3.21 Reconnect call

    The Reconnect Call service will clear a specified connection at the
    reconnecting device and retrieve a specified held connection at the
    same device. This service can be handled by using the action
    <terminate/ to terminate an existing call and using
    <Media:mediaupdate/ and <dequeue to retrieve a held call.

 17.3.22 Retrieve call

    The Retrieve Call service connects a specified held connection.  This
    can be handled by <dequeue and <Media:mediaupdate/ actions.

 17.3.23 Send message

    The Send Message service allows the computing function to send a
    message to one or more devices. The message, composed of one or more
    MIME body parts, is included in the Send Message service request.
    This service can be used to send messages for many different types of
    applications (Instant Messaging, Email, Pager, and Short Message
    Service (SMS), etc). In LESS, we use <Message:sendmsg/ action to
    send a message, and <Email:send/ to send an email.

 17.3.24 Single step conference call

    The Single Step Conference Call joins a new device into an existing
    call.  This service can be repeated to make n-device conference calls
    (subject to switching function limits). This can be handled by the
    action <merge/.

 17.3.25 Single step transfer call

    The Single Step Transfer Call service transfers an existing
    connection at a device to another device. This transfer is performed



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    in a single-step, that is the device doing the transfer does not have
    to place the existing call on hold before issuing the Single Step
    Transfer Call service.  This can be handled by the action
    <transfer/.

 17.3.26 Transfer call

    The Transfer Call service transfers a call held at a device to an
    active call at the same device. The held and active calls at the
    transferring device shall be merged into a new call. Also, the
    Connections of the held and active calls at the transferring device
    shall become Null and their ConnectionIDs shall be released (i.e.,
    the transferring device is no longer involved with the call). This
    service is in fact merge a held call and an existing call into a 3-
    way calling. It should be handled by LESS <merge action.

 17.4 New services

    One of the biggest advantage of Internet telephony is its ability to
    easily integrate other Internet services, such as presence
    information, email, and web. The integration can introduce many new
    services which are impossible for PSTN networks. These new services
    are not mentioned in Q.1211 or 5ESS service documents.

 17.4.1 Email

    For email, we usually care about three things, receivers, subject,
    and content. We can use <location or <lookup modifier to specify
    receivers, use subject parameter in <email action for subject
    information, and put content as the data of an <email tag.  For
    example,


    <location url="mailto:bob@example.com"
      <Email:send subject="This is a test"
        We simply send this as a test for our LESS scripts.
      </Email:send
    </location



    There is no output of the email action.

 17.4.2 Web

    There are two parameters for a web service action, one is the URI to
    visit, the other is the HTTP method. The URI parameter can be handled
    by the <location and <lookup modifiers. We use different action to



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    represent different HTTP methods. For example, <Web:get represents
    HTTP GET method, <Web:post represents HTTP POST method. Below is a
    service example,


    <location uri="http://www.example.com"
      <Web:get/
    </location



    The output of the a web action can be succeed, redirect, or failed.

 17.4.3 Instant messaging

    People use instant messaging as a complementary communication method
    for voice call and email. We introduce two toplevel actions
    <IM::message-coming for incoming message, <UI:command
    command="sendmsg" for an outgoing message, and one action
    <IM::sendmsg for sending a message out. For example,


    <less
      <IM:message-coming
        <address-switch field="origin"
          <address is="sip:bob@example.com"
            <location url="sip:bob@example.com"
              <IM:sendmsgHi, Bob</IM:sendmsg
            </location
          </address
        </address-switch
      </IM:message-coming
    </less



 17.4.4 Event subscription and notification

    Below is an example for address-based event subscription handling.


    <Event:subscription
      <address-switch field="origin"
        <address is="sip:bob@example.com"
          <Event:approve
            <next
              <Event:notify status="closed"/
            </next



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          </Event:approve
        </address
      </address-switch
    </Event:subscription



 17.4.5 Event notification and event-based services

    Event notifications can trigger many new services. For example,


    <Event:notification
      <address-switch field="origin"
        <address is="sip:bob@example.com"
          <Event:event-switch
            <Event:event status="online"
              <location url="sip:bob@example.com"
                <call/
              </location
            </Event:event
          </Event:event-switch
        </address
      </address-switch
    </Event:notification



 17.4.6 Location-based services

    Location information gets more and more important in people's
    communications.  It is not only used for tracking, but also for
    guarding appropriate communication behaviors, triggering
    communication actions, and discovering available resources in a
    context.  Below is an example showing location-based call decision
    making.


    <incoming
      <Location:where-switch
        <Location:where placytype="movie-theatre"
          <alert style="vibrate"/
        </Location:where
      </Location:where-switch
    </incoming






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 18 Feature Interaction Handling Algorithm for LESS Scripts

    For LESS-based services, due to the tree-like structure of LESS, we
    consider it simple and efficient to design an algorithm to merge
    multiple LESS decision trees into one.  After merging, for a specific
    trigger, there is only one active LESS script at a device. The
    merging algorithm is good for single component services. For service
    scripts on different devices, for example, the single user multiple
    components (SUMC) call control services the merging algorithm can
    only detect feature interactions, it cannot merge all the scripts
    into one to resolve the interactions. After merging, we will still
    keep the original scripts so users can modify them independently.
    This way, no conflicts in service execution because for a given
    trigger, it only needs to go through one decision tree to perform
    services.  In the mean time, we can still ensure the service
    modularity so users can create their services efficiently.

 18.1 Tree merging algorithm

    The overall multi-script merging process is as below.


    set base-rule-set empty
    foreach LESS-tree {
     convert the LESS-tree into a rule set
     foreach rule in the rule set {
      normalize the rule
     }
     merge the normalized rule set into base-rule-set
    }
    convert base-rule-set into a decision tree



    The merging operation is in fact to merge every set of rules into
    base-rule-set, then convert the base-rule-set back to a decision
    tree. We will explain every step of the process below.

    A rule of a LESS decision tree is defined as which actions get
    executed under a certain condition for a specific trigger. Based on
    the LESS design principles we introduced in Section 2.1, the path
    from the root of a decision tree to each leaf node consists a
    decision rule.  We construct a rule as a composition of a trigger,
    the actions in accordance to the trigger, and a list of switch nodes
    that in the path from the root to the action node, we name the list
    of switch nodes rule path.  For example, for the script below, we can
    represent a decision rule as "{incoming,accept,{{string-
    switch,organization="ABC Inc."},{address-switch,



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    origin="sip:tom@abc.com"},{string-switch,subject="group meeting"}}}".


    <less
      <incoming
        <string-switch field="organization"
          <string is="ABC Inc."
            <address-switch field="origin"
              <address is="sip:tom@abc.com"
                <string-switch field="subject"
                  <string is="group meeting"
                    <accept/
                  </string
                </string-switch
              </address
              <otherwise
                <location url="sip:tom@voicemail.abc.com"
                  <redirect/
                </location
              </otherwise
            </address-switch
          </string
        </string-switch
      </incoming
    </less



    To facilitate rule merging, we need to normalize the rules generated
    from LESS decision trees. The normalization process sorts rule paths
    to a specific order, e.g., in the order of "address-switch", "time-
    switch", "status-switch", "string-switch", "priority-switch",
    "where-switch", and "language-switch". It will also merge the switch
    nodes with the same switch name into one node in a rule path.  For
    example, a normalized rule for the script above is "{incoming,
    accept, {address-switch, origin="sip:tom@abc.com"},
    {string-switch, subject="ABC group meeting", organization="ABC
    Inc."}}".  Because switches are independent of each other, normalized
    rules are functionally equal to original rules.  After normalization,
    we can follow the process below to detect feature interactions
    between two normalized rules.


    if (two rules have different triggers) {
     no rule conflict
    } elseif actions in two rules do not conflict {
     no rule conflict
    } elseif no overlap between rule path in two rules {



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     no rule conflict
    } else {
     two rules conflict with each other,
     return the rule path overlap and action conflict information
     prompt to the script owner to judge
    }



    During the process, we use the action conflict table defined in our
    technical report "Feature Interactions in Internet Telephony End
    Systems" [15]. to check whether two actions interact with each other
    or not. If actions in two rules conflict with each other, we need to
    check whether there are conditions matching both rule paths.  We name
    this kind of conditions the overlap between two rule paths.  We
    employ the following algorithm to get the overlap.


    set overlap-set empty
    foreach switch-node1 in rule-path1 {
     if there is a switch-node2 in rule-path2 has the same switch name {
      if the switch-overlap between switch-node1 and switch-node2 is empty {
       return empty overlap-set
      } else {
       insert the switch-overlap into overlap-set
      }
     } else {
      insert switch-node1 into overlap-set
     }
    }
    foreach switch-node2 in rule-path2 {
     if there is not a switch-node1 in rule-path1 has the same switch name {
      insert switch-node2 into overlap-set
     }
    }
    return overlap-set



    During the overlap handling process, different switch types have
    different overlap detection method. We will not detail the overlap
    handling for each switch type in this paper.

    Once we find the overlap-set and the conflicting actions, we can
    present the information to users to make decisions.  We can record
    the decision made by the user and build a normalized rule set without
    conflicts.




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    To convert a set of normalized rules back to a decision tree is
    straightforward. The pseudo code below shows the algorithm.


    set tree empty
    foreach rule in the merged rule set {
     foreach switch node in the rule path {
      //since each rule is normalized, the switch node appears in order
      go along the tree from the root
      if the switch node matches a tree node {
       go to the matched branch, and continue for the next switch node
      } else {
       if there is an unmatched branch {
        go to unmatched branch, continue the test
       } else {
        create an unmatched branch
        put the rest rule path (including current switch node)
        in the unmatched branch
       }}}}



 19 The XML Schema for LESS and Commonly Used Extensions

 19.1 XML Schema for LESS


























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    <?xml version="1.0" encoding="UTF-8"?
    <!-- edited with XMLSPY v2004 rel. 2 U (http://www.xmlspy.com) by Xiaotao Wu (Columbia University Computer Science Dept) --
    <xs:schema targetNamespace="urn:ietf:params:xml:ns:less" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns="urn:ietf:params:xml:ns:less" elementFormDefault="qualified" attributeFormDefault="unqualified"
      <xs:complexType name="TriggerType" abstract="true"
        <xs:group ref="Node"/
      </xs:complexType
      <xs:element name="trigger" type="TriggerType"/
      <xs:complexType name="ActionType" abstract="true" mixed="true"
        <xs:all
          <xs:element name="next" minOccurs="0"
            <xs:complexType
              <xs:group ref="Node"/
            </xs:complexType
          </xs:element
        </xs:all
      </xs:complexType
      <xs:element name="action" type="ActionType"/
      <xs:complexType name="SwitchType" abstract="true"/
      <xs:element name="switch" type="SwitchType"/
      <xs:complexType name="ModifierType" abstract="true"/
      <xs:element name="modifier" type="ModifierType"/
      <xs:complexType name="SubAction"
        <xs:attribute name="ref" type="xs:string" use="required"/
      </xs:complexType
      <xs:element name="sub" type="SubAction"/
      <xs:complexType name="SubactionType"
        <xs:group ref="Node"/
        <xs:attribute name="id" use="required"/
      </xs:complexType
      <xs:complexType name="AncillaryType"/
      <xs:group name="Node"
        <xs:choice
          <xs:element ref="switch" minOccurs="0"/
          <xs:element ref="modifier" minOccurs="0" maxOccurs="unbounded"/
          <xs:element ref="sub" minOccurs="0"/
          <xs:element ref="action" minOccurs="0" maxOccurs="unbounded"/
        </xs:choice
      </xs:group
      <xs:complexType name="OtherwiseAction"
        <xs:group ref="Node"/
      </xs:complexType
      <xs:complexType name="NotPresentAction"
        <xs:group ref="Node"/
      </xs:complexType
      <xs:complexType name="LESSType"
        <xs:sequence
          <xs:element name="ancillary" type="AncillaryType" minOccurs="0"/



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          <xs:element name="subaction" type="SubactionType" minOccurs="0" maxOccurs="unbounded"/
          <xs:element ref="trigger" minOccurs="0" maxOccurs="unbounded"
            <xs:annotation
              <xs:documentationAny toplevel action MUST NOT appear more than once.</xs:documentation
            </xs:annotation
          </xs:element
        </xs:sequence
      </xs:complexType
      <xs:element name="less" type="LESSType"/
      <xs:simpleType name="YesNoType"
        <xs:restriction base="xs:NMTOKEN"
          <xs:enumeration value="yes"/
          <xs:enumeration value="no"/
        </xs:restriction
      </xs:simpleType
      <xs:simpleType name="StatusType"
        <xs:union
          <xs:simpleType
            <xs:restriction base="xs:NMTOKEN"
              <xs:enumeration value="busy"/
              <xs:enumeration value="notfound"/
              <xs:enumeration value="reject"/
              <xs:enumeration value="error"/
            </xs:restriction
          </xs:simpleType
          <xs:simpleType
            <xs:restriction base="xs:string"/
          </xs:simpleType
        </xs:union
      </xs:simpleType
      <xs:complexType name="IncomingType"
        <xs:complexContent
          <xs:extension base="TriggerType"/
        </xs:complexContent
      </xs:complexType
      <xs:element name="incoming" type="IncomingType" substitutionGroup="trigger"/
      <xs:complexType name="TimerType"
        <xs:complexContent
          <xs:extension base="TriggerType"
            <xs:attribute name="dtstart" type="xs:string" use="required"
              <xs:annotation
                <xs:documentationRFC 2445 DATE-TIME</xs:documentation
              </xs:annotation
            </xs:attribute
            <xs:attribute name="dtend" type="xs:string" use="optional"
              <xs:annotation
                <xs:documentationRFC 2445 DATE-TIME</xs:documentation
              </xs:annotation



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            </xs:attribute
            <xs:attribute name="duration" type="xs:string" use="optional"
              <xs:annotation
                <xs:documentationRFC 2445 DURATION</xs:documentation
              </xs:annotation
            </xs:attribute
            <xs:attribute name="freq" type="FreqType" use="optional"/
            <xs:attribute name="interval" type="xs:positiveInteger" default="1"/
            <xs:attribute name="until" type="xs:string" use="optional"
              <xs:annotation
                <xs:documentationRFC 2445 DATE-TIME</xs:documentation
              </xs:annotation
            </xs:attribute
            <xs:attribute name="count" type="xs:positiveInteger" use="optional"/
            <xs:attribute name="bysecond" type="xs:string" use="optional"
              <xs:annotation
                <xs:documentationComma-separated list of seconds within a minute. Valid values are 0 to 59.</xs:documentation
              </xs:annotation
            </xs:attribute
            <xs:attribute name="byminute" type="xs:string" use="optional"
              <xs:annotation
                <xs:documentationComma-separated list of minutes within an hour. Valid values are 0 to 59.</xs:documentation
              </xs:annotation
            </xs:attribute
            <xs:attribute name="byhour" type="xs:string" use="optional"
              <xs:annotation
                <xs:documentationComma-separated list of hours of the day. Valid values are 0 to 23.</xs:documentation
              </xs:annotation
            </xs:attribute
            <xs:attribute name="byday" type="xs:string" use="optional"
              <xs:annotation
                <xs:documentationComma-separated list of days of the week. Valid values are "MO", "TU", "WE", "TH", "FR", "SA" and "SU". These values are not case-sensitive. Each can be preceded by a positive (+n) or negative (-n) integer.</xs:documentation
              </xs:annotation
            </xs:attribute
            <xs:attribute name="bymonthday" type="xs:string" use="optional"
              <xs:annotation
                <xs:documentationComma-separated list of days of the month. Valid values are 1 to 31 or -31 to -1.</xs:documentation
              </xs:annotation
            </xs:attribute
            <xs:attribute name="byyearday" type="xs:string" use="optional"
              <xs:annotation
                <xs:documentationComma-separated list of days of the year. Valid values are 1 to 366 or -366 to -1.</xs:documentation
              </xs:annotation
            </xs:attribute
            <xs:attribute name="byweekno" type="xs:string" use="optional"
              <xs:annotation
                <xs:documentationComma-separated list of ordinals specifying weeks of the year. Valid values are 1 to 53 or -53 to -1.</xs:documentation
              </xs:annotation



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            </xs:attribute
            <xs:attribute name="bymonth" type="xs:string" use="optional"
              <xs:annotation
                <xs:documentationComma-separated list of months of the year. Valid values are 1 to 12.</xs:documentation
              </xs:annotation
            </xs:attribute
            <xs:attribute name="wkst" type="DayType" default="MO"/
            <xs:attribute name="bysetpos" type="YearDayType"/
            <xs:anyAttribute namespace="##any" processContents="lax"/
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="timer" type="TimerType" substitutionGroup="trigger"/
      <xs:simpleType name="OrderingType"
        <xs:restriction base="xs:NMTOKEN"
          <xs:enumeration value="parallel"/
          <xs:enumeration value="sequential"/
          <xs:enumeration value="first-only"/
        </xs:restriction
      </xs:simpleType
      <xs:simpleType name="AddressFieldType"
        <xs:union
          <xs:simpleType
            <xs:restriction base="xs:NMTOKEN"
              <xs:enumeration value="origin"/
              <xs:enumeration value="destination"/
              <xs:enumeration value="original-destination"/
            </xs:restriction
          </xs:simpleType
          <xs:simpleType
            <xs:restriction base="xs:string"/
          </xs:simpleType
        </xs:union
      </xs:simpleType
      <xs:simpleType name="AddressSubfieldType"
        <xs:union
          <xs:simpleType
            <xs:restriction base="xs:NMTOKEN"
              <xs:enumeration value="address-type"/
              <xs:enumeration value="user"/
              <xs:enumeration value="host"/
              <xs:enumeration value="port"/
              <xs:enumeration value="tel"/
              <xs:enumeration value="display"/
              <xs:enumeration value="password"/
              <xs:enumeration value="alias-type"/
            </xs:restriction
          </xs:simpleType



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          <xs:simpleType
            <xs:restriction base="xs:string"/
          </xs:simpleType
        </xs:union
      </xs:simpleType
      <xs:complexType name="AddressType"
        <xs:annotation
          <xs:documentationExactly one of the three attributes must appear</xs:documentation
        </xs:annotation
        <xs:group ref="Node"/
        <xs:attribute name="is" type="xs:string" use="optional"/
        <xs:attribute name="contains" type="xs:string" use="optional"
          <xs:annotation
            <xs:documentationfor "display" only</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="subdomain-of" type="xs:string" use="optional"
          <xs:annotation
            <xs:documentationfor "host", "tel" only</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:anyAttribute namespace="##any" processContents="lax"/
      </xs:complexType
      <xs:complexType name="AddressSwitchType"
        <xs:complexContent
          <xs:extension base="SwitchType"
            <xs:sequence
              <xs:element name="address" type="AddressType" minOccurs="0" maxOccurs="unbounded"/
              <xs:sequence minOccurs="0"
                <xs:element name="not-present" type="NotPresentAction"/
                <xs:element name="address" type="AddressType" minOccurs="0" maxOccurs="unbounded"/
              </xs:sequence
              <xs:element name="otherwise" type="OtherwiseAction" minOccurs="0"/
            </xs:sequence
            <xs:attribute name="field" type="AddressFieldType" use="required"/
            <xs:attribute name="subfield" type="AddressSubfieldType" use="optional"/
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="address-switch" type="AddressSwitchType" substitutionGroup="switch"/
      <xs:simpleType name="StringFieldType"
        <xs:restriction base="xs:NMTOKEN"
          <xs:enumeration value="subject"/
          <xs:enumeration value="organization"/
          <xs:enumeration value="user-agent"/
          <xs:enumeration value="display"/
        </xs:restriction
      </xs:simpleType



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      <xs:complexType name="StringType"
        <xs:group ref="Node"/
        <xs:attribute name="is" type="xs:string" use="optional"/
        <xs:attribute name="contains" type="xs:string" use="optional"/
        <xs:anyAttribute namespace="##any" processContents="lax"/
      </xs:complexType
      <xs:complexType name="StringSwitchType"
        <xs:complexContent
          <xs:extension base="SwitchType"
            <xs:sequence
              <xs:element name="string" type="StringType" minOccurs="0" maxOccurs="unbounded"/
              <xs:sequence minOccurs="0"
                <xs:element name="not-present" type="NotPresentAction"/
                <xs:element name="string" type="StringType" minOccurs="0" maxOccurs="unbounded"/
              </xs:sequence
              <xs:element name="otherwise" type="OtherwiseAction" minOccurs="0"/
            </xs:sequence
            <xs:attribute name="field" type="StringFieldType" use="required"
              <xs:annotation
                <xs:documentationStrings are matched as case-insensitive Unicode strings.</xs:documentation
              </xs:annotation
            </xs:attribute
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="string-switch" type="StringSwitchType" substitutionGroup="switch"/
      <xs:complexType name="LanguageType"
        <xs:group ref="Node"/
        <xs:attribute name="matches" type="xs:string" use="required"
          <xs:annotation
            <xs:documentationThe value of one of these parameters is a language-tag, as defined in RFC 3066.</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:anyAttribute namespace="##any" processContents="lax"/
      </xs:complexType
      <xs:complexType name="LanguageSwitchType"
        <xs:complexContent
          <xs:extension base="SwitchType"
            <xs:sequence
              <xs:element name="language" type="LanguageType" minOccurs="0" maxOccurs="unbounded"/
              <xs:sequence minOccurs="0"
                <xs:element name="not-present" type="NotPresentAction"/
                <xs:element name="language" type="LanguageType" minOccurs="0" maxOccurs="unbounded"/
              </xs:sequence
              <xs:element name="otherwise" type="OtherwiseAction" minOccurs="0"/
            </xs:sequence
          </xs:extension
        </xs:complexContent



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      </xs:complexType
      <xs:element name="language-switch" type="LanguageSwitchType" substitutionGroup="switch"/
      <xs:simpleType name="FreqType"
        <xs:restriction base="xs:NMTOKEN"
          <xs:pattern value="[s|S][e|E][c|C][o|O][n|N][d|D][l|L][y|Y]"/
          <xs:pattern value="[m|M][i|I][n|N][u|U][t|T][e|E][l|L][y|Y]"/
          <xs:pattern value="[h|H][o|O][u|U][r|R][l|L][y|Y]"/
          <xs:pattern value="[d|D][a|A][i|I][l|L][y|Y]"/
          <xs:pattern value="[w|W][e|E][e|E][k|K][l|L][y|Y]"/
          <xs:pattern value="[m|M][o|N][n|N][t|T][h|H][l|L][y|Y]"/
          <xs:pattern value="[y|Y][e|E][a|A][r|R][l|L][y|Y]"/
        </xs:restriction
      </xs:simpleType
      <xs:simpleType name="YearDayType"
        <xs:union
          <xs:simpleType
            <xs:restriction base="xs:integer"
              <xs:minInclusive value="-366"/
              <xs:maxInclusive value="-1"/
            </xs:restriction
          </xs:simpleType
          <xs:simpleType
            <xs:restriction base="xs:integer"
              <xs:minInclusive value="1"/
              <xs:maxExclusive value="366"/
            </xs:restriction
          </xs:simpleType
        </xs:union
      </xs:simpleType
      <xs:simpleType name="DayType"
        <xs:restriction base="xs:NMTOKEN"
          <xs:pattern value="[m|M][o|O]"/
          <xs:pattern value="[t|T][u|U]"/
          <xs:pattern value="[w|W][e|E]"/
          <xs:pattern value="[t|T][h|H]"/
          <xs:pattern value="[f|F][r|R]"/
          <xs:pattern value="[s|S][a|A]"/
          <xs:pattern value="[s|S][u|U]"/
        </xs:restriction
      </xs:simpleType
      <xs:complexType name="TimeType"
        <xs:annotation
          <xs:documentationExactly one of the two attributes "dtend" and "duration" must occur. None of the attributes following freq are meaningful unless freq appears. </xs:documentation
        </xs:annotation
        <xs:group ref="Node"/
        <xs:attribute name="dtstart" type="xs:string" use="required"
          <xs:annotation
            <xs:documentationRFC 2445 DATE-TIME</xs:documentation



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          </xs:annotation
        </xs:attribute
        <xs:attribute name="dtend" type="xs:string" use="optional"
          <xs:annotation
            <xs:documentationRFC 2445 DATE-TIME</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="duration" type="xs:string" use="optional"
          <xs:annotation
            <xs:documentationRFC 2445 DURATION</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="freq" type="FreqType" use="optional"/
        <xs:attribute name="interval" type="xs:positiveInteger" default="1"/
        <xs:attribute name="until" type="xs:string" use="optional"
          <xs:annotation
            <xs:documentationRFC 2445 DATE-TIME</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="count" type="xs:positiveInteger" use="optional"/
        <xs:attribute name="bysecond" type="xs:string" use="optional"
          <xs:annotation
            <xs:documentationComma-separated list of seconds within a minute. Valid values are 0 to 59.</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="byminute" type="xs:string" use="optional"
          <xs:annotation
            <xs:documentationComma-separated list of minutes within an hour. Valid values are 0 to 59.</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="byhour" type="xs:string" use="optional"
          <xs:annotation
            <xs:documentationComma-separated list of hours of the day. Valid values are 0 to 23.</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="byday" type="xs:string" use="optional"
          <xs:annotation
            <xs:documentationComma-separated list of days of the week. Valid values are "MO", "TU", "WE", "TH", "FR", "SA" and "SU". These values are not case-sensitive. Each can be preceded by a positive (+n) or negative (-n) integer.</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="bymonthday" type="xs:string" use="optional"
          <xs:annotation
            <xs:documentationComma-separated list of days of the month. Valid values are 1 to 31 or -31 to -1.</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="byyearday" type="xs:string" use="optional"
          <xs:annotation
            <xs:documentationComma-separated list of days of the year. Valid values are 1 to 366 or -366 to -1.</xs:documentation



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          </xs:annotation
        </xs:attribute
        <xs:attribute name="byweekno" type="xs:string" use="optional"
          <xs:annotation
            <xs:documentationComma-separated list of ordinals specifying weeks of the year. Valid values are 1 to 53 or -53 to -1.</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="bymonth" type="xs:string" use="optional"
          <xs:annotation
            <xs:documentationComma-separated list of months of the year. Valid values are 1 to 12.</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="wkst" type="DayType" default="MO"/
        <xs:attribute name="bysetpos" type="YearDayType"/
        <xs:anyAttribute namespace="##any" processContents="lax"/
      </xs:complexType
      <xs:simpleType name="TZIDType"
        <xs:restriction base="xs:string"/
      </xs:simpleType
      <xs:simpleType name="TZURLType"
        <xs:restriction base="xs:anyURI"/
      </xs:simpleType
      <xs:complexType name="TimeSwitchType"
        <xs:complexContent
          <xs:extension base="SwitchType"
            <xs:sequence
              <xs:element name="time" type="TimeType" minOccurs="0" maxOccurs="unbounded"/
              <xs:sequence minOccurs="0"
                <xs:element name="not-present" type="NotPresentAction"/
                <xs:element name="time" type="TimeType" minOccurs="0" maxOccurs="unbounded"/
              </xs:sequence
              <xs:element name="otherwise" type="OtherwiseAction" minOccurs="0"/
            </xs:sequence
            <xs:attribute name="tzid" type="TZIDType"/
            <xs:attribute name="tzurl" type="TZURLType"/
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="time-switch" type="TimeSwitchType" substitutionGroup="switch"/
      <xs:simpleType name="PriorityValues"
        <xs:restriction base="xs:NMTOKEN"
          <xs:pattern value="[e|E][m|M][e|E][r|R][g|G][e|E][n|N][c|C][y|Y]"/
          <xs:pattern value="[u|U][r|R][g|G][e|E][n|N][t|T]"/
          <xs:pattern value="[n|N][o|O][r|R][m|M][a|A][l|L]"/
          <xs:pattern value="[n|N][o|O][n|N]-[u|U][r|R][g|G][e|E][n|N][t|T]"/
        </xs:restriction
      </xs:simpleType
      <xs:complexType name="PriorityType"



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        <xs:annotation
          <xs:documentationExactly one of the three attributes must appear </xs:documentation
        </xs:annotation
        <xs:group ref="Node"/
        <xs:attribute name="less" type="PriorityValues"/
        <xs:attribute name="greater" type="PriorityValues"/
        <xs:attribute name="equal" type="xs:string"
          <xs:annotation
            <xs:documentationcase-insensitive</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:anyAttribute namespace="##any" processContents="lax"/
      </xs:complexType
      <xs:complexType name="PrioritySwitchType"
        <xs:complexContent
          <xs:extension base="SwitchType"
            <xs:sequence
              <xs:element name="priority" type="PriorityType" minOccurs="0" maxOccurs="unbounded"/
              <xs:sequence minOccurs="0"
                <xs:element name="not-present" type="NotPresentAction"/
                <xs:element name="priority" type="PriorityType" minOccurs="0" maxOccurs="unbounded"/
              </xs:sequence
              <xs:element name="otherwise" type="OtherwiseAction" minOccurs="0"/
            </xs:sequence
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="priority-switch" type="PrioritySwitchType" substitutionGroup="switch"/
      <xs:complexType name="UserStatusType"
        <xs:group ref="Node"/
        <xs:attribute name="less" type="xs:integer"/
        <xs:attribute name="greater" type="xs:integer"/
        <xs:attribute name="equal" type="xs:integer"/
        <xs:attribute name="is"
          <xs:simpleType
            <xs:list itemType="xs:string"/
          </xs:simpleType
        </xs:attribute
        <xs:attribute name="contains"
          <xs:simpleType
            <xs:list itemType="xs:string"/
          </xs:simpleType
        </xs:attribute
      </xs:complexType
      <xs:complexType name="StatusSwitchType"
        <xs:complexContent
          <xs:extension base="SwitchType"
            <xs:sequence



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              <xs:element name="status" type="UserStatusType" minOccurs="0" maxOccurs="unbounded"/
              <xs:sequence minOccurs="0"
                <xs:element name="not-present" type="NotPresentAction"/
                <xs:element name="status" type="UserStatusType" minOccurs="0" maxOccurs="unbounded"/
              </xs:sequence
              <xs:element name="otherwise" type="OtherwiseAction" minOccurs="0"/
            </xs:sequence
            <xs:attribute name="uri" type="xs:anyURI" use="optional"/
            <xs:attribute name="status-name"
              <xs:simpleType
                <xs:restriction base="xs:NMTOKEN"
                  <xs:enumeration value="active-calls"/
                  <xs:enumeration value="presence"/
                  <xs:enumeration value="activity"/
                  <xs:enumeration value="mood"/
                </xs:restriction
              </xs:simpleType
            </xs:attribute
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="status-switch" type="StatusSwitchType" substitutionGroup="switch"/
      <xs:simpleType name="LocationPriorityType"
        <xs:restriction base="xs:float"
          <xs:minInclusive value="0.0"/
          <xs:maxInclusive value="1.0"/
        </xs:restriction
      </xs:simpleType
      <xs:complexType name="LocationType"
        <xs:complexContent
          <xs:extension base="ModifierType"
            <xs:group ref="Node"/
            <xs:attribute name="url" type="xs:anyURI" use="required"/
            <xs:attribute name="priority" type="LocationPriorityType" use="optional" default="1.0"/
            <xs:attribute name="clear" type="YesNoType" default="no"/
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="location" type="LocationType" substitutionGroup="modifier"/
      <xs:complexType name="LookupType"
        <xs:complexContent
          <xs:extension base="ModifierType"
            <xs:all
              <xs:element name="success" minOccurs="0"
                <xs:complexType
                  <xs:group ref="Node"/
                </xs:complexType
              </xs:element



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              <xs:element name="notfound" minOccurs="0"
                <xs:complexType
                  <xs:group ref="Node"/
                </xs:complexType
              </xs:element
              <xs:element name="failure" minOccurs="0"
                <xs:complexType
                  <xs:group ref="Node"/
                </xs:complexType
              </xs:element
            </xs:all
            <xs:attribute name="source" type="xs:string" use="required"/
            <xs:attribute name="order" use="optional" default="parallel"
              <xs:simpleType
                <xs:restriction base="xs:NMTOKEN"
                  <xs:enumeration value="parallel"/
                  <xs:enumeration value="sequential"/
                </xs:restriction
              </xs:simpleType
            </xs:attribute
            <xs:attribute name="timeout" type="xs:positiveInteger" default="30"/
            <xs:attribute name="clear" type="YesNoType" default="no"/
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="lookup" type="LookupType" substitutionGroup="modifier"/
      <xs:complexType name="RemoveLocationType"
        <xs:complexContent
          <xs:extension base="ModifierType"
            <xs:group ref="Node"/
            <xs:attribute name="location" type="xs:string" use="optional"/
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="remove-location" type="RemoveLocationType" substitutionGroup="modifier"/
      <xs:complexType name="LogAction"
        <xs:complexContent
          <xs:extension base="ActionType"
            <xs:group ref="Node"/
            <xs:attribute name="name" type="xs:string" use="optional"/
            <xs:attribute name="comment" type="xs:string" use="optional"/
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="log" type="LogAction" substitutionGroup="action"/
      <xs:complexType name="MailAction"
        <xs:complexContent
          <xs:extension base="ActionType"



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            <xs:group ref="Node"/
            <xs:attribute name="url" type="xs:anyURI" use="required"/
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="mail" type="MailAction" substitutionGroup="action"/
      <xs:complexType name="WaitAction"
        <xs:complexContent
          <xs:extension base="ActionType"
            <xs:group ref="Node"/
            <xs:attribute name="duration" type="xs:duration" use="required"/
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="wait" type="WaitAction" substitutionGroup="action"/
      <xs:complexType name="AcceptActionType"
        <xs:complexContent
          <xs:extension base="ActionType"/
        </xs:complexContent
      </xs:complexType
      <xs:element name="accept" type="AcceptActionType" substitutionGroup="action"/
      <xs:complexType name="RedirectAction"
        <xs:complexContent
          <xs:extension base="ActionType"
            <xs:attribute name="permanent" type="YesNoType" default="no"/
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="redirect" type="RedirectAction" substitutionGroup="action"/
      <xs:complexType name="RejectAction"
        <xs:complexContent
          <xs:extension base="ActionType"
            <xs:attribute name="status" type="StatusType" use="required"/
            <xs:attribute name="reason" type="xs:string" use="optional"/
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="reject" type="RejectAction" substitutionGroup="action"/
      <xs:complexType name="AuthenticateAction"
        <xs:complexContent
          <xs:extension base="ActionType"
            <xs:all
              <xs:element name="success" minOccurs="0"
                <xs:complexType
                  <xs:group ref="Node"/
                </xs:complexType
              </xs:element
              <xs:element name="failure" minOccurs="0"



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                <xs:complexType
                  <xs:group ref="Node"/
                </xs:complexType
              </xs:element
            </xs:all
            <xs:attribute name="method" use="optional" default="digest"
              <xs:simpleType
                <xs:restriction base="xs:NMTOKEN"
                  <xs:enumeration value="digest"/
                  <xs:enumeration value="basic"/
                </xs:restriction
              </xs:simpleType
            </xs:attribute
            <xs:attribute name="realm" type="xs:string"/
            <xs:attribute name="user" type="xs:string"/
            <xs:attribute name="target"
              <xs:simpleType
                <xs:restriction base="xs:NMTOKEN"
                  <xs:enumeration value="remote"/
                  <xs:enumeration value="local"/
                </xs:restriction
              </xs:simpleType
            </xs:attribute
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="authenticate" type="AuthenticateAction" substitutionGroup="action"/
      <xs:complexType name="CallActionType"
        <xs:complexContent
          <xs:extension base="ActionType"
            <xs:all
              <xs:element name="accepted" minOccurs="0"
                <xs:complexType
                  <xs:group ref="Node"/
                </xs:complexType
              </xs:element
              <xs:element name="busy" minOccurs="0"
                <xs:complexType
                  <xs:group ref="Node"/
                </xs:complexType
              </xs:element
              <xs:element name="noanswer" minOccurs="0"
                <xs:complexType
                  <xs:group ref="Node"/
                </xs:complexType
              </xs:element
              <xs:element name="failure" minOccurs="0"
                <xs:complexType



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                  <xs:group ref="Node"/
                </xs:complexType
              </xs:element
              <xs:element name="redirection" minOccurs="0"
                <xs:complexType
                  <xs:group ref="Node"/
                </xs:complexType
              </xs:element
            </xs:all
            <xs:attribute name="timeout" type="xs:positiveInteger"/
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="call" type="CallActionType" substitutionGroup="action"/
      <xs:complexType name="TerminateActionType"
        <xs:complexContent
          <xs:extension base="ActionType"
            <xs:group ref="Node"/
            <xs:attribute name="uri"
              <xs:simpleType
                <xs:list itemType="xs:anyURI"/
              </xs:simpleType
            </xs:attribute
            <xs:attribute name="subject"
              <xs:simpleType
                <xs:list itemType="xs:string"/
              </xs:simpleType
            </xs:attribute
            <xs:attribute name="calls"
              <xs:simpleType
                <xs:restriction base="xs:NMTOKEN"
                  <xs:enumeration value="all"/
                  <xs:enumeration value="last"/
                  <xs:enumeration value="this"/
                </xs:restriction
              </xs:simpleType
            </xs:attribute
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="terminate" type="TerminateActionType" substitutionGroup="action"/
    </xs:schema


 19.2 XML Schema for LESS Media Extension






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    <?xml version="1.0" encoding="UTF-8"?
    <!-- edited with XMLSPY v2004 rel. 2 U (http://www.xmlspy.com) by Xiaotao Wu (Columbia University Computer Science Dept) --
    <xs:schema targetNamespace="urn:ietf:params:xml:ns:less" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns="urn:ietf:params:xml:ns:less" elementFormDefault="qualified" attributeFormDefault="unqualified"
      <xs:complexType name="TriggerType" abstract="true"
        <xs:group ref="Node"/
      </xs:complexType
      <xs:element name="trigger" type="TriggerType"/
      <xs:complexType name="ActionType" abstract="true" mixed="true"
        <xs:all
          <xs:element name="next" minOccurs="0"
            <xs:complexType
              <xs:group ref="Node"/
            </xs:complexType
          </xs:element
        </xs:all
      </xs:complexType
      <xs:element name="action" type="ActionType"/
      <xs:complexType name="SwitchType" abstract="true"/
      <xs:element name="switch" type="SwitchType"/
      <xs:complexType name="ModifierType" abstract="true"/
      <xs:element name="modifier" type="ModifierType"/
      <xs:complexType name="SubAction"
        <xs:attribute name="ref" type="xs:string" use="required"/
      </xs:complexType
      <xs:element name="sub" type="SubAction"/
      <xs:complexType name="SubactionType"
        <xs:group ref="Node"/
        <xs:attribute name="id" use="required"/
      </xs:complexType
      <xs:complexType name="AncillaryType"/
      <xs:group name="Node"
        <xs:choice
          <xs:element ref="switch" minOccurs="0"/
          <xs:element ref="modifier" minOccurs="0" maxOccurs="unbounded"/
          <xs:element ref="sub" minOccurs="0"/
          <xs:element ref="action" minOccurs="0" maxOccurs="unbounded"/
        </xs:choice
      </xs:group
      <xs:complexType name="OtherwiseAction"
        <xs:group ref="Node"/
      </xs:complexType
      <xs:complexType name="NotPresentAction"
        <xs:group ref="Node"/
      </xs:complexType
      <xs:complexType name="LESSType"
        <xs:sequence
          <xs:element name="ancillary" type="AncillaryType" minOccurs="0"/



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          <xs:element name="subaction" type="SubactionType" minOccurs="0" maxOccurs="unbounded"/
          <xs:element ref="trigger" minOccurs="0" maxOccurs="unbounded"
            <xs:annotation
              <xs:documentationAny toplevel action MUST NOT appear more than once.</xs:documentation
            </xs:annotation
          </xs:element
        </xs:sequence
      </xs:complexType
      <xs:element name="less" type="LESSType"/
      <xs:simpleType name="YesNoType"
        <xs:restriction base="xs:NMTOKEN"
          <xs:enumeration value="yes"/
          <xs:enumeration value="no"/
        </xs:restriction
      </xs:simpleType
      <xs:simpleType name="StatusType"
        <xs:union
          <xs:simpleType
            <xs:restriction base="xs:NMTOKEN"
              <xs:enumeration value="busy"/
              <xs:enumeration value="notfound"/
              <xs:enumeration value="reject"/
              <xs:enumeration value="error"/
            </xs:restriction
          </xs:simpleType
          <xs:simpleType
            <xs:restriction base="xs:string"/
          </xs:simpleType
        </xs:union
      </xs:simpleType
      <xs:complexType name="IncomingType"
        <xs:complexContent
          <xs:extension base="TriggerType"/
        </xs:complexContent
      </xs:complexType
      <xs:element name="incoming" type="IncomingType" substitutionGroup="trigger"/
      <xs:complexType name="TimerType"
        <xs:complexContent
          <xs:extension base="TriggerType"
            <xs:attribute name="dtstart" type="xs:string" use="required"
              <xs:annotation
                <xs:documentationRFC 2445 DATE-TIME</xs:documentation
              </xs:annotation
            </xs:attribute
            <xs:attribute name="dtend" type="xs:string" use="optional"
              <xs:annotation
                <xs:documentationRFC 2445 DATE-TIME</xs:documentation
              </xs:annotation



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            </xs:attribute
            <xs:attribute name="duration" type="xs:string" use="optional"
              <xs:annotation
                <xs:documentationRFC 2445 DURATION</xs:documentation
              </xs:annotation
            </xs:attribute
            <xs:attribute name="freq" type="FreqType" use="optional"/
            <xs:attribute name="interval" type="xs:positiveInteger" default="1"/
            <xs:attribute name="until" type="xs:string" use="optional"
              <xs:annotation
                <xs:documentationRFC 2445 DATE-TIME</xs:documentation
              </xs:annotation
            </xs:attribute
            <xs:attribute name="count" type="xs:positiveInteger" use="optional"/
            <xs:attribute name="bysecond" type="xs:string" use="optional"
              <xs:annotation
                <xs:documentationComma-separated list of seconds within a minute. Valid values are 0 to 59.</xs:documentation
              </xs:annotation
            </xs:attribute
            <xs:attribute name="byminute" type="xs:string" use="optional"
              <xs:annotation
                <xs:documentationComma-separated list of minutes within an hour. Valid values are 0 to 59.</xs:documentation
              </xs:annotation
            </xs:attribute
            <xs:attribute name="byhour" type="xs:string" use="optional"
              <xs:annotation
                <xs:documentationComma-separated list of hours of the day. Valid values are 0 to 23.</xs:documentation
              </xs:annotation
            </xs:attribute
            <xs:attribute name="byday" type="xs:string" use="optional"
              <xs:annotation
                <xs:documentationComma-separated list of days of the week. Valid values are "MO", "TU", "WE", "TH", "FR", "SA" and "SU". These values are not case-sensitive. Each can be preceded by a positive (+n) or negative (-n) integer.</xs:documentation
              </xs:annotation
            </xs:attribute
            <xs:attribute name="bymonthday" type="xs:string" use="optional"
              <xs:annotation
                <xs:documentationComma-separated list of days of the month. Valid values are 1 to 31 or -31 to -1.</xs:documentation
              </xs:annotation
            </xs:attribute
            <xs:attribute name="byyearday" type="xs:string" use="optional"
              <xs:annotation
                <xs:documentationComma-separated list of days of the year. Valid values are 1 to 366 or -366 to -1.</xs:documentation
              </xs:annotation
            </xs:attribute
            <xs:attribute name="byweekno" type="xs:string" use="optional"
              <xs:annotation
                <xs:documentationComma-separated list of ordinals specifying weeks of the year. Valid values are 1 to 53 or -53 to -1.</xs:documentation
              </xs:annotation



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            </xs:attribute
            <xs:attribute name="bymonth" type="xs:string" use="optional"
              <xs:annotation
                <xs:documentationComma-separated list of months of the year. Valid values are 1 to 12.</xs:documentation
              </xs:annotation
            </xs:attribute
            <xs:attribute name="wkst" type="DayType" default="MO"/
            <xs:attribute name="bysetpos" type="YearDayType"/
            <xs:anyAttribute namespace="##any" processContents="lax"/
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="timer" type="TimerType" substitutionGroup="trigger"/
      <xs:simpleType name="OrderingType"
        <xs:restriction base="xs:NMTOKEN"
          <xs:enumeration value="parallel"/
          <xs:enumeration value="sequential"/
          <xs:enumeration value="first-only"/
        </xs:restriction
      </xs:simpleType
      <xs:simpleType name="AddressFieldType"
        <xs:union
          <xs:simpleType
            <xs:restriction base="xs:NMTOKEN"
              <xs:enumeration value="origin"/
              <xs:enumeration value="destination"/
              <xs:enumeration value="original-destination"/
            </xs:restriction
          </xs:simpleType
          <xs:simpleType
            <xs:restriction base="xs:string"/
          </xs:simpleType
        </xs:union
      </xs:simpleType
      <xs:simpleType name="AddressSubfieldType"
        <xs:union
          <xs:simpleType
            <xs:restriction base="xs:NMTOKEN"
              <xs:enumeration value="address-type"/
              <xs:enumeration value="user"/
              <xs:enumeration value="host"/
              <xs:enumeration value="port"/
              <xs:enumeration value="tel"/
              <xs:enumeration value="display"/
              <xs:enumeration value="password"/
              <xs:enumeration value="alias-type"/
            </xs:restriction
          </xs:simpleType



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          <xs:simpleType
            <xs:restriction base="xs:string"/
          </xs:simpleType
        </xs:union
      </xs:simpleType
      <xs:complexType name="AddressType"
        <xs:annotation
          <xs:documentationExactly one of the three attributes must appear</xs:documentation
        </xs:annotation
        <xs:group ref="Node"/
        <xs:attribute name="is" type="xs:string" use="optional"/
        <xs:attribute name="contains" type="xs:string" use="optional"
          <xs:annotation
            <xs:documentationfor "display" only</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="subdomain-of" type="xs:string" use="optional"
          <xs:annotation
            <xs:documentationfor "host", "tel" only</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:anyAttribute namespace="##any" processContents="lax"/
      </xs:complexType
      <xs:complexType name="AddressSwitchType"
        <xs:complexContent
          <xs:extension base="SwitchType"
            <xs:sequence
              <xs:element name="address" type="AddressType" minOccurs="0" maxOccurs="unbounded"/
              <xs:sequence minOccurs="0"
                <xs:element name="not-present" type="NotPresentAction"/
                <xs:element name="address" type="AddressType" minOccurs="0" maxOccurs="unbounded"/
              </xs:sequence
              <xs:element name="otherwise" type="OtherwiseAction" minOccurs="0"/
            </xs:sequence
            <xs:attribute name="field" type="AddressFieldType" use="required"/
            <xs:attribute name="subfield" type="AddressSubfieldType" use="optional"/
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="address-switch" type="AddressSwitchType" substitutionGroup="switch"/
      <xs:simpleType name="StringFieldType"
        <xs:restriction base="xs:NMTOKEN"
          <xs:enumeration value="subject"/
          <xs:enumeration value="organization"/
          <xs:enumeration value="user-agent"/
          <xs:enumeration value="display"/
        </xs:restriction
      </xs:simpleType



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      <xs:complexType name="StringType"
        <xs:group ref="Node"/
        <xs:attribute name="is" type="xs:string" use="optional"/
        <xs:attribute name="contains" type="xs:string" use="optional"/
        <xs:anyAttribute namespace="##any" processContents="lax"/
      </xs:complexType
      <xs:complexType name="StringSwitchType"
        <xs:complexContent
          <xs:extension base="SwitchType"
            <xs:sequence
              <xs:element name="string" type="StringType" minOccurs="0" maxOccurs="unbounded"/
              <xs:sequence minOccurs="0"
                <xs:element name="not-present" type="NotPresentAction"/
                <xs:element name="string" type="StringType" minOccurs="0" maxOccurs="unbounded"/
              </xs:sequence
              <xs:element name="otherwise" type="OtherwiseAction" minOccurs="0"/
            </xs:sequence
            <xs:attribute name="field" type="StringFieldType" use="required"
              <xs:annotation
                <xs:documentationStrings are matched as case-insensitive Unicode strings.</xs:documentation
              </xs:annotation
            </xs:attribute
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="string-switch" type="StringSwitchType" substitutionGroup="switch"/
      <xs:complexType name="LanguageType"
        <xs:group ref="Node"/
        <xs:attribute name="matches" type="xs:string" use="required"
          <xs:annotation
            <xs:documentationThe value of one of these parameters is a language-tag, as defined in RFC 3066.</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:anyAttribute namespace="##any" processContents="lax"/
      </xs:complexType
      <xs:complexType name="LanguageSwitchType"
        <xs:complexContent
          <xs:extension base="SwitchType"
            <xs:sequence
              <xs:element name="language" type="LanguageType" minOccurs="0" maxOccurs="unbounded"/
              <xs:sequence minOccurs="0"
                <xs:element name="not-present" type="NotPresentAction"/
                <xs:element name="language" type="LanguageType" minOccurs="0" maxOccurs="unbounded"/
              </xs:sequence
              <xs:element name="otherwise" type="OtherwiseAction" minOccurs="0"/
            </xs:sequence
          </xs:extension
        </xs:complexContent



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      </xs:complexType
      <xs:element name="language-switch" type="LanguageSwitchType" substitutionGroup="switch"/
      <xs:simpleType name="FreqType"
        <xs:restriction base="xs:NMTOKEN"
          <xs:pattern value="[s|S][e|E][c|C][o|O][n|N][d|D][l|L][y|Y]"/
          <xs:pattern value="[m|M][i|I][n|N][u|U][t|T][e|E][l|L][y|Y]"/
          <xs:pattern value="[h|H][o|O][u|U][r|R][l|L][y|Y]"/
          <xs:pattern value="[d|D][a|A][i|I][l|L][y|Y]"/
          <xs:pattern value="[w|W][e|E][e|E][k|K][l|L][y|Y]"/
          <xs:pattern value="[m|M][o|N][n|N][t|T][h|H][l|L][y|Y]"/
          <xs:pattern value="[y|Y][e|E][a|A][r|R][l|L][y|Y]"/
        </xs:restriction
      </xs:simpleType
      <xs:simpleType name="YearDayType"
        <xs:union
          <xs:simpleType
            <xs:restriction base="xs:integer"
              <xs:minInclusive value="-366"/
              <xs:maxInclusive value="-1"/
            </xs:restriction
          </xs:simpleType
          <xs:simpleType
            <xs:restriction base="xs:integer"
              <xs:minInclusive value="1"/
              <xs:maxExclusive value="366"/
            </xs:restriction
          </xs:simpleType
        </xs:union
      </xs:simpleType
      <xs:simpleType name="DayType"
        <xs:restriction base="xs:NMTOKEN"
          <xs:pattern value="[m|M][o|O]"/
          <xs:pattern value="[t|T][u|U]"/
          <xs:pattern value="[w|W][e|E]"/
          <xs:pattern value="[t|T][h|H]"/
          <xs:pattern value="[f|F][r|R]"/
          <xs:pattern value="[s|S][a|A]"/
          <xs:pattern value="[s|S][u|U]"/
        </xs:restriction
      </xs:simpleType
      <xs:complexType name="TimeType"
        <xs:annotation
          <xs:documentationExactly one of the two attributes "dtend" and "duration" must occur. None of the attributes following freq are meaningful unless freq appears. </xs:documentation
        </xs:annotation
        <xs:group ref="Node"/
        <xs:attribute name="dtstart" type="xs:string" use="required"
          <xs:annotation
            <xs:documentationRFC 2445 DATE-TIME</xs:documentation



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          </xs:annotation
        </xs:attribute
        <xs:attribute name="dtend" type="xs:string" use="optional"
          <xs:annotation
            <xs:documentationRFC 2445 DATE-TIME</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="duration" type="xs:string" use="optional"
          <xs:annotation
            <xs:documentationRFC 2445 DURATION</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="freq" type="FreqType" use="optional"/
        <xs:attribute name="interval" type="xs:positiveInteger" default="1"/
        <xs:attribute name="until" type="xs:string" use="optional"
          <xs:annotation
            <xs:documentationRFC 2445 DATE-TIME</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="count" type="xs:positiveInteger" use="optional"/
        <xs:attribute name="bysecond" type="xs:string" use="optional"
          <xs:annotation
            <xs:documentationComma-separated list of seconds within a minute. Valid values are 0 to 59.</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="byminute" type="xs:string" use="optional"
          <xs:annotation
            <xs:documentationComma-separated list of minutes within an hour. Valid values are 0 to 59.</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="byhour" type="xs:string" use="optional"
          <xs:annotation
            <xs:documentationComma-separated list of hours of the day. Valid values are 0 to 23.</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="byday" type="xs:string" use="optional"
          <xs:annotation
            <xs:documentationComma-separated list of days of the week. Valid values are "MO", "TU", "WE", "TH", "FR", "SA" and "SU". These values are not case-sensitive. Each can be preceded by a positive (+n) or negative (-n) integer.</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="bymonthday" type="xs:string" use="optional"
          <xs:annotation
            <xs:documentationComma-separated list of days of the month. Valid values are 1 to 31 or -31 to -1.</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="byyearday" type="xs:string" use="optional"
          <xs:annotation
            <xs:documentationComma-separated list of days of the year. Valid values are 1 to 366 or -366 to -1.</xs:documentation



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          </xs:annotation
        </xs:attribute
        <xs:attribute name="byweekno" type="xs:string" use="optional"
          <xs:annotation
            <xs:documentationComma-separated list of ordinals specifying weeks of the year. Valid values are 1 to 53 or -53 to -1.</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="bymonth" type="xs:string" use="optional"
          <xs:annotation
            <xs:documentationComma-separated list of months of the year. Valid values are 1 to 12.</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="wkst" type="DayType" default="MO"/
        <xs:attribute name="bysetpos" type="YearDayType"/
        <xs:anyAttribute namespace="##any" processContents="lax"/
      </xs:complexType
      <xs:simpleType name="TZIDType"
        <xs:restriction base="xs:string"/
      </xs:simpleType
      <xs:simpleType name="TZURLType"
        <xs:restriction base="xs:anyURI"/
      </xs:simpleType
      <xs:complexType name="TimeSwitchType"
        <xs:complexContent
          <xs:extension base="SwitchType"
            <xs:sequence
              <xs:element name="time" type="TimeType" minOccurs="0" maxOccurs="unbounded"/
              <xs:sequence minOccurs="0"
                <xs:element name="not-present" type="NotPresentAction"/
                <xs:element name="time" type="TimeType" minOccurs="0" maxOccurs="unbounded"/
              </xs:sequence
              <xs:element name="otherwise" type="OtherwiseAction" minOccurs="0"/
            </xs:sequence
            <xs:attribute name="tzid" type="TZIDType"/
            <xs:attribute name="tzurl" type="TZURLType"/
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="time-switch" type="TimeSwitchType" substitutionGroup="switch"/
      <xs:simpleType name="PriorityValues"
        <xs:restriction base="xs:NMTOKEN"
          <xs:pattern value="[e|E][m|M][e|E][r|R][g|G][e|E][n|N][c|C][y|Y]"/
          <xs:pattern value="[u|U][r|R][g|G][e|E][n|N][t|T]"/
          <xs:pattern value="[n|N][o|O][r|R][m|M][a|A][l|L]"/
          <xs:pattern value="[n|N][o|O][n|N]-[u|U][r|R][g|G][e|E][n|N][t|T]"/
        </xs:restriction
      </xs:simpleType
      <xs:complexType name="PriorityType"



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        <xs:annotation
          <xs:documentationExactly one of the three attributes must appear </xs:documentation
        </xs:annotation
        <xs:group ref="Node"/
        <xs:attribute name="less" type="PriorityValues"/
        <xs:attribute name="greater" type="PriorityValues"/
        <xs:attribute name="equal" type="xs:string"
          <xs:annotation
            <xs:documentationcase-insensitive</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:anyAttribute namespace="##any" processContents="lax"/
      </xs:complexType
      <xs:complexType name="PrioritySwitchType"
        <xs:complexContent
          <xs:extension base="SwitchType"
            <xs:sequence
              <xs:element name="priority" type="PriorityType" minOccurs="0" maxOccurs="unbounded"/
              <xs:sequence minOccurs="0"
                <xs:element name="not-present" type="NotPresentAction"/
                <xs:element name="priority" type="PriorityType" minOccurs="0" maxOccurs="unbounded"/
              </xs:sequence
              <xs:element name="otherwise" type="OtherwiseAction" minOccurs="0"/
            </xs:sequence
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="priority-switch" type="PrioritySwitchType" substitutionGroup="switch"/
      <xs:complexType name="UserStatusType"
        <xs:group ref="Node"/
        <xs:attribute name="less" type="xs:integer"/
        <xs:attribute name="greater" type="xs:integer"/
        <xs:attribute name="equal" type="xs:integer"/
        <xs:attribute name="is"
          <xs:simpleType
            <xs:list itemType="xs:string"/
          </xs:simpleType
        </xs:attribute
        <xs:attribute name="contains"
          <xs:simpleType
            <xs:list itemType="xs:string"/
          </xs:simpleType
        </xs:attribute
      </xs:complexType
      <xs:complexType name="StatusSwitchType"
        <xs:complexContent
          <xs:extension base="SwitchType"
            <xs:sequence



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              <xs:element name="status" type="UserStatusType" minOccurs="0" maxOccurs="unbounded"/
              <xs:sequence minOccurs="0"
                <xs:element name="not-present" type="NotPresentAction"/
                <xs:element name="status" type="UserStatusType" minOccurs="0" maxOccurs="unbounded"/
              </xs:sequence
              <xs:element name="otherwise" type="OtherwiseAction" minOccurs="0"/
            </xs:sequence
            <xs:attribute name="uri" type="xs:anyURI" use="optional"/
            <xs:attribute name="status-name"
              <xs:simpleType
                <xs:restriction base="xs:NMTOKEN"
                  <xs:enumeration value="active-calls"/
                  <xs:enumeration value="presence"/
                  <xs:enumeration value="activity"/
                  <xs:enumeration value="mood"/
                </xs:restriction
              </xs:simpleType
            </xs:attribute
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="status-switch" type="StatusSwitchType" substitutionGroup="switch"/
      <xs:simpleType name="LocationPriorityType"
        <xs:restriction base="xs:float"
          <xs:minInclusive value="0.0"/
          <xs:maxInclusive value="1.0"/
        </xs:restriction
      </xs:simpleType
      <xs:complexType name="LocationType"
        <xs:complexContent
          <xs:extension base="ModifierType"
            <xs:group ref="Node"/
            <xs:attribute name="url" type="xs:anyURI" use="required"/
            <xs:attribute name="priority" type="LocationPriorityType" use="optional" default="1.0"/
            <xs:attribute name="clear" type="YesNoType" default="no"/
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="location" type="LocationType" substitutionGroup="modifier"/
      <xs:complexType name="LookupType"
        <xs:complexContent
          <xs:extension base="ModifierType"
            <xs:all
              <xs:element name="success" minOccurs="0"
                <xs:complexType
                  <xs:group ref="Node"/
                </xs:complexType
              </xs:element



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              <xs:element name="notfound" minOccurs="0"
                <xs:complexType
                  <xs:group ref="Node"/
                </xs:complexType
              </xs:element
              <xs:element name="failure" minOccurs="0"
                <xs:complexType
                  <xs:group ref="Node"/
                </xs:complexType
              </xs:element
            </xs:all
            <xs:attribute name="source" type="xs:string" use="required"/
            <xs:attribute name="order" use="optional" default="parallel"
              <xs:simpleType
                <xs:restriction base="xs:NMTOKEN"
                  <xs:enumeration value="parallel"/
                  <xs:enumeration value="sequential"/
                </xs:restriction
              </xs:simpleType
            </xs:attribute
            <xs:attribute name="timeout" type="xs:positiveInteger" default="30"/
            <xs:attribute name="clear" type="YesNoType" default="no"/
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="lookup" type="LookupType" substitutionGroup="modifier"/
      <xs:complexType name="RemoveLocationType"
        <xs:complexContent
          <xs:extension base="ModifierType"
            <xs:group ref="Node"/
            <xs:attribute name="location" type="xs:string" use="optional"/
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="remove-location" type="RemoveLocationType" substitutionGroup="modifier"/
      <xs:complexType name="LogAction"
        <xs:complexContent
          <xs:extension base="ActionType"
            <xs:group ref="Node"/
            <xs:attribute name="name" type="xs:string" use="optional"/
            <xs:attribute name="comment" type="xs:string" use="optional"/
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="log" type="LogAction" substitutionGroup="action"/
      <xs:complexType name="MailAction"
        <xs:complexContent
          <xs:extension base="ActionType"



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            <xs:group ref="Node"/
            <xs:attribute name="url" type="xs:anyURI" use="required"/
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="mail" type="MailAction" substitutionGroup="action"/
      <xs:complexType name="WaitAction"
        <xs:complexContent
          <xs:extension base="ActionType"
            <xs:group ref="Node"/
            <xs:attribute name="duration" type="xs:duration" use="required"/
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="wait" type="WaitAction" substitutionGroup="action"/
      <xs:complexType name="AcceptActionType"
        <xs:complexContent
          <xs:extension base="ActionType"/
        </xs:complexContent
      </xs:complexType
      <xs:element name="accept" type="AcceptActionType" substitutionGroup="action"/
      <xs:complexType name="RedirectAction"
        <xs:complexContent
          <xs:extension base="ActionType"
            <xs:attribute name="permanent" type="YesNoType" default="no"/
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="redirect" type="RedirectAction" substitutionGroup="action"/
      <xs:complexType name="RejectAction"
        <xs:complexContent
          <xs:extension base="ActionType"
            <xs:attribute name="status" type="StatusType" use="required"/
            <xs:attribute name="reason" type="xs:string" use="optional"/
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="reject" type="RejectAction" substitutionGroup="action"/
      <xs:complexType name="AuthenticateAction"
        <xs:complexContent
          <xs:extension base="ActionType"
            <xs:all
              <xs:element name="success" minOccurs="0"
                <xs:complexType
                  <xs:group ref="Node"/
                </xs:complexType
              </xs:element
              <xs:element name="failure" minOccurs="0"



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                <xs:complexType
                  <xs:group ref="Node"/
                </xs:complexType
              </xs:element
            </xs:all
            <xs:attribute name="method" use="optional" default="digest"
              <xs:simpleType
                <xs:restriction base="xs:NMTOKEN"
                  <xs:enumeration value="digest"/
                  <xs:enumeration value="basic"/
                </xs:restriction
              </xs:simpleType
            </xs:attribute
            <xs:attribute name="realm" type="xs:string"/
            <xs:attribute name="user" type="xs:string"/
            <xs:attribute name="target"
              <xs:simpleType
                <xs:restriction base="xs:NMTOKEN"
                  <xs:enumeration value="remote"/
                  <xs:enumeration value="local"/
                </xs:restriction
              </xs:simpleType
            </xs:attribute
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="authenticate" type="AuthenticateAction" substitutionGroup="action"/
      <xs:complexType name="CallActionType"
        <xs:complexContent
          <xs:extension base="ActionType"
            <xs:all
              <xs:element name="accepted" minOccurs="0"
                <xs:complexType
                  <xs:group ref="Node"/
                </xs:complexType
              </xs:element
              <xs:element name="busy" minOccurs="0"
                <xs:complexType
                  <xs:group ref="Node"/
                </xs:complexType
              </xs:element
              <xs:element name="noanswer" minOccurs="0"
                <xs:complexType
                  <xs:group ref="Node"/
                </xs:complexType
              </xs:element
              <xs:element name="failure" minOccurs="0"
                <xs:complexType



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                  <xs:group ref="Node"/
                </xs:complexType
              </xs:element
              <xs:element name="redirection" minOccurs="0"
                <xs:complexType
                  <xs:group ref="Node"/
                </xs:complexType
              </xs:element
            </xs:all
            <xs:attribute name="timeout" type="xs:positiveInteger"/
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="call" type="CallActionType" substitutionGroup="action"/
      <xs:complexType name="TerminateActionType"
        <xs:complexContent
          <xs:extension base="ActionType"
            <xs:group ref="Node"/
            <xs:attribute name="uri"
              <xs:simpleType
                <xs:list itemType="xs:anyURI"/
              </xs:simpleType
            </xs:attribute
            <xs:attribute name="subject"
              <xs:simpleType
                <xs:list itemType="xs:string"/
              </xs:simpleType
            </xs:attribute
            <xs:attribute name="calls"
              <xs:simpleType
                <xs:restriction base="xs:NMTOKEN"
                  <xs:enumeration value="all"/
                  <xs:enumeration value="last"/
                  <xs:enumeration value="this"/
                </xs:restriction
              </xs:simpleType
            </xs:attribute
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="terminate" type="TerminateActionType" substitutionGroup="action"/
    </xs:schema


 19.3 XML Schema for LESS Mid-call handling Extension






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    <?xml version="1.0" encoding="UTF-8"?
    <!-- edited with XMLSPY v2004 rel. 2 U (http://www.xmlspy.com) by Xiaotao Wu (Columbia University Computer Science Dept) --
    <!-- edited with XML Spy v4.3 U (http://www.xmlspy.com) by Xiaotao Wu (Columbia University) --
    <xs:schema targetNamespace="urn:ietf:params:xml:ns:less:midcall" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:LESS="urn:ietf:params:xml:ns:less" xmlns="urn:ietf:params:xml:ns:less:midcall"
      <xs:import namespace="urn:ietf:params:xml:ns:less" schemaLocation="less.xsd"/
      <xs:complexType name="TransferActionType"
        <xs:complexContent
          <xs:extension base="LESS:ActionType"
            <xs:all
              <xs:element name="accepted" minOccurs="0"
                <xs:complexType
                  <xs:group ref="Node"/
                </xs:complexType
              </xs:element
              <xs:element name="busy" minOccurs="0"
                <xs:complexType
                  <xs:group ref="Node"/
                </xs:complexType
              </xs:element
              <xs:element name="noanswer" minOccurs="0"
                <xs:complexType
                  <xs:group ref="Node"/
                </xs:complexType
              </xs:element
              <xs:element name="failure" minOccurs="0"
                <xs:complexType
                  <xs:group ref="Node"/
                </xs:complexType
              </xs:element
              <xs:element name="redirection" minOccurs="0"
                <xs:complexType
                  <xs:group ref="Node"/
                </xs:complexType
              </xs:element
            </xs:all
            <xs:attribute name="timeout" type="xs:positiveInteger" use="optional" default="20"/
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="transfer" type="TransferActionType" substitutionGroup="LESS:action"/
      <xs:complexType name="MergeAction"
        <xs:complexContent
          <xs:extension base="LESS:ActionType"
            <xs:attribute name="uri"
              <xs:simpleType
                <xs:list itemType="xs:anyURI"/
              </xs:simpleType



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            </xs:attribute
            <xs:attribute name="subject"
              <xs:simpleType
                <xs:list itemType="xs:string"/
              </xs:simpleType
            </xs:attribute
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="merge" type="MergeAction" substitutionGroup="LESS:action"/
    </xs:schema


 19.4 XML Schema for LESS User Interaction Extension





































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    <?xml version="1.0" encoding="UTF-8"?
    <!-- edited with XMLSPY v2004 rel. 2 U (http://www.xmlspy.com) by Xiaotao Wu (Columbia University Computer Science Dept) --
    <!-- edited with XML Spy v4.3 U (http://www.xmlspy.com) by Xiaotao Wu (Columbia University) --
    <xs:schema targetNamespace="urn:ietf:params:xml:ns:less:ui" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:LESS="urn:ietf:params:xml:ns:less" xmlns="urn:ietf:params:xml:ns:less:ui"
      <xs:import namespace="urn:ietf:params:xml:ns:less" schemaLocation="less.xsd"/
      <xs:complexType name="CommandType"
        <xs:complexContent
          <xs:extension base="LESS:TriggerType"
            <xs:attribute name="command" type="xs:string" use="required"/
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="command" type="CommandType" substitutionGroup="LESS:trigger"/
      <xs:complexType name="AlertActionType"
        <xs:complexContent
          <xs:extension base="LESS:ActionType"
            <xs:all
              <xs:element name="timeout" minOccurs="0"
                <xs:complexType
                  <xs:group ref="Node"/
                </xs:complexType
              </xs:element
            </xs:all
            <xs:attribute name="duration" type="xs:dateTime" use="optional"/
            <xs:attribute name="priority" type="LESS:PriorityValues" use="optional"/
            <xs:attribute name="message" type="xs:string" use="optional"/
            <xs:attribute name="icon" type="xs:string" use="optional"/
            <xs:attribute name="input" type="xs:anyURI" use="optional"/
            <xs:attribute name="style" use="optional" default="sound"
              <xs:simpleType
                <xs:list
                  <xs:simpleType
                    <xs:restriction base="xs:string"
                      <xs:enumeration value="viberate"/
                      <xs:enumeration value="flash"/
                      <xs:enumeration value="sound"/
                      <xs:enumeration value="text"/
                    </xs:restriction
                  </xs:simpleType
                </xs:list
              </xs:simpleType
            </xs:attribute
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="alert" type="AlertActionType" substitutionGroup="LESS:action"/
      <xs:complexType name="GetinputActionType"



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        <xs:complexContent
          <xs:extension base="LESS:ActionType"
            <xs:all
              <xs:element name="noanswer" minOccurs="0"
                <xs:complexType
                  <xs:group ref="Node"/
                </xs:complexType
              </xs:element
            </xs:all
            <xs:attribute name="timeout" type="xs:duration" use="optional"/
            <xs:attribute name="source" use="optional"
              <xs:simpleType
                <xs:restriction base="xs:NMTOKEN"
                  <xs:enumeration value="screen"/
                  <xs:enumeration value="audio"/
                </xs:restriction
              </xs:simpleType
            </xs:attribute
            <xs:attribute name="target" use="optional"
              <xs:simpleType
                <xs:restriction base="xs:NMTOKEN"
                  <xs:enumeration value="remote"/
                  <xs:enumeration value="local"/
                </xs:restriction
              </xs:simpleType
            </xs:attribute
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="getinput" type="GetinputActionType" substitutionGroup="LESS:action"/
    </xs:schema


 19.5 XML Schema for LESS Instant Messaging Extension

















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    <?xml version="1.0" encoding="UTF-8"?
    <!-- edited with XMLSPY v2004 rel. 2 U (http://www.xmlspy.com) by Xiaotao Wu (Columbia University Computer Science Dept) --
    <!-- edited with XML Spy v4.3 U (http://www.xmlspy.com) by Xiaotao Wu (Columbia University) --
    <xs:schema targetNamespace="urn:ietf:params:xml:ns:less:im" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:LESS="urn:ietf:params:xml:ns:less" xmlns="urn:ietf:params:xml:ns:less:im"
      <xs:import namespace="urn:ietf:params:xml:ns:less" schemaLocation="less.xsd"/
      <xs:complexType name="MessageType"
        <xs:complexContent
          <xs:extension base="LESS:TriggerType"/
        </xs:complexContent
      </xs:complexType
      <xs:element name="message" type="MessageType" substitutionGroup="LESS:trigger"/
      <xs:complexType name="SendmsgActionType"
        <xs:complexContent
          <xs:extension base="LESS:ActionType"
            <xs:attribute name="type"
              <xs:simpleType
                <xs:union
                  <xs:simpleType
                    <xs:restriction base="xs:NMTOKEN"
                      <xs:enumeration value="dtmf"/
                      <xs:enumeration value="text"/
                      <xs:enumeration value="image"/
                      <xs:enumeration value="file"/
                    </xs:restriction
                  </xs:simpleType
                  <xs:simpleType
                    <xs:restriction base="xs:string"/
                  </xs:simpleType
                </xs:union
              </xs:simpleType
            </xs:attribute
            <xs:attribute name="message" type="xs:string"/
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="sendmsg" type="SendmsgActionType" substitutionGroup="LESS:action"/
    </xs:schema


 19.6 XML Schema for LESS Event Handling Extension










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    <?xml version="1.0" encoding="UTF-8"?
    <!-- edited with XMLSPY v2004 rel. 2 U (http://www.xmlspy.com) by Xiaotao Wu (Columbia University Computer Science Dept) --
    <xs:schema targetNamespace="urn:ietf:params:xml:ns:less:event" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:LESS="urn:ietf:params:xml:ns:less" xmlns="urn:ietf:params:xml:ns:less:event" elementFormDefault="qualified" attributeFormDefault="unqualified"
      <xs:import namespace="urn:ietf:params:xml:ns:less" schemaLocation="less.xsd"/
      <xs:element name="subscription" type="SubscriptionType" substitutionGroup="LESS:trigger"/
      <xs:complexType name="SubscriptionType"
        <xs:complexContent
          <xs:extension base="LESS:TriggerType"/
        </xs:complexContent
      </xs:complexType
      <xs:element name="notification" type="NotificationType" substitutionGroup="LESS:trigger"/
      <xs:complexType name="NotificationType"
        <xs:complexContent
          <xs:extension base="LESS:TriggerType"/
        </xs:complexContent
      </xs:complexType
      <xs:complexType name="EventType"
        <xs:group ref="LESS:Node"/
        <xs:attribute name="package" use="required"
          <xs:simpleType
            <xs:list itemType="xs:string"/
          </xs:simpleType
        </xs:attribute
        <xs:attribute name="is" use="optional"
          <xs:simpleType
            <xs:list itemType="xs:string"/
          </xs:simpleType
        </xs:attribute
      </xs:complexType
      <xs:complexType name="EventSwitchType"
        <xs:sequence
          <xs:element name="event" type="EventType" minOccurs="0" maxOccurs="unbounded"/
          <xs:sequence minOccurs="0"
            <xs:element name="not-present" type="LESS:NotPresentAction"/
            <xs:element name="event" type="EventType" minOccurs="0" maxOccurs="unbounded"/
          </xs:sequence
          <xs:element name="otherwise" type="LESS:OtherwiseAction" minOccurs="0"/
        </xs:sequence
      </xs:complexType
      <xs:element name="event-switch" type="EventSwitchType" substitutionGroup="LESS:switch"/
      <xs:complexType name="ApproveActionType"
        <xs:complexContent
          <xs:extension base="LESS:ActionType"
            <xs:attribute name="expires" type="xs:integer"
              <xs:annotation
                <xs:documentationExpiration in seconds</xs:documentation
              </xs:annotation



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            </xs:attribute
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="approve" type="ApproveActionType" substitutionGroup="LESS:action"/
      <xs:complexType name="DenyActionType"
        <xs:complexContent
          <xs:extension base="LESS:ActionType"
            <xs:attribute name="reason" type="xs:string" use="optional"/
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="deny" type="DenyActionType" substitutionGroup="LESS:action"/
      <xs:complexType name="DeferActionType"
        <xs:complexContent
          <xs:extension base="LESS:ActionType"/
        </xs:complexContent
      </xs:complexType
      <xs:element name="defer" type="DeferActionType" substitutionGroup="LESS:action"/
      <xs:complexType name="SubscribeActionType"
        <xs:complexContent
          <xs:extension base="LESS:ActionType"
            <xs:all
              <xs:element name="approved" minOccurs="0"
                <xs:complexType
                  <xs:group ref="LESS:Node"/
                </xs:complexType
              </xs:element
              <xs:element name="denied" minOccurs="0"
                <xs:complexType
                  <xs:group ref="LESS:Node"/
                </xs:complexType
              </xs:element
              <xs:element name="pending" minOccurs="0"
                <xs:complexType
                  <xs:group ref="LESS:Node"/
                </xs:complexType
              </xs:element
              <xs:element name="redirection" minOccurs="0"
                <xs:complexType
                  <xs:group ref="LESS:Node"/
                </xs:complexType
              </xs:element
              <xs:element name="noanswer" minOccurs="0"
                <xs:complexType
                  <xs:group ref="LESS:Node"/
                </xs:complexType
              </xs:element



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              <xs:element name="failure" minOccurs="0"
                <xs:complexType
                  <xs:group ref="LESS:Node"/
                </xs:complexType
              </xs:element
            </xs:all
            <xs:attribute name="timeout" type="xs:positiveInteger" use="optional" default="20"/
            <xs:attribute name="expires" type="xs:integer"
              <xs:annotation
                <xs:documentationExpiration in seconds</xs:documentation
              </xs:annotation
            </xs:attribute
            <xs:attribute name="package" type="xs:string" use="required"/
            <xs:attribute name="content" type="xs:string" use="optional"/
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="subscribe" type="SubscribeActionType" substitutionGroup="LESS:action"/
      <xs:complexType name="NotifyActionType"
        <xs:complexContent
          <xs:extension base="LESS:ActionType"
            <xs:all
              <xs:element name="accepted" minOccurs="0"
                <xs:complexType
                  <xs:group ref="LESS:Node"/
                </xs:complexType
              </xs:element
              <xs:element name="redirection" minOccurs="0"
                <xs:complexType
                  <xs:group ref="LESS:Node"/
                </xs:complexType
              </xs:element
              <xs:element name="noanswer" minOccurs="0"
                <xs:complexType
                  <xs:group ref="LESS:Node"/
                </xs:complexType
              </xs:element
              <xs:element name="failure" minOccurs="0"
                <xs:complexType
                  <xs:group ref="LESS:Node"/
                </xs:complexType
              </xs:element
            </xs:all
            <xs:attribute name="timeout" type="xs:positiveInteger" use="optional" default="20"/
            <xs:attribute name="package" type="xs:string" use="required"/
            <xs:attribute name="event" type="xs:string" use="required"/
            <xs:anyAttribute namespace="##any" processContents="lax"/
          </xs:extension



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        </xs:complexContent
      </xs:complexType
      <xs:element name="notify" type="NotifyActionType" substitutionGroup="LESS:action"/
    </xs:schema


 19.7 XML Schema for LESS Location-based Services Extension












































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    <?xml version="1.0" encoding="UTF-8"?
    <!-- edited with XMLSPY v2004 rel. 2 U (http://www.xmlspy.com) by Xiaotao Wu (Columbia University Computer Science Dept) --
    <xs:schema targetNamespace="urn:ietf:params:xml:ns:less:location" xmlns="urn:ietf:params:xml:ns:less:location" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:LESS="urn:ietf:params:xml:ns:less" elementFormDefault="qualified" attributeFormDefault="unqualified"
      <xs:import namespace="urn:ietf:params:xml:ns:less" schemaLocation="less.xsd"/
      <xs:complexType name="WhereSwitchType"
        <xs:sequence
          <xs:element name="where" type="WhereType" minOccurs="0" maxOccurs="unbounded"/
          <xs:sequence minOccurs="0"
            <xs:element name="not-present" type="LESS:NotPresentAction"/
            <xs:element name="where" type="WhereType" minOccurs="0" maxOccurs="unbounded"/
          </xs:sequence
          <xs:element name="otherwise" type="LESS:OtherwiseAction" minOccurs="0"/
        </xs:sequence
        <xs:attribute name="type" use="required"
          <xs:simpleType
            <xs:restriction base="xs:string"
              <xs:enumeration value="geospatial"/
              <xs:enumeration value="civil"/
            </xs:restriction
          </xs:simpleType
        </xs:attribute
        <xs:attribute name="uri" type="xs:anyURI"/
      </xs:complexType
      <xs:element name="where-switch" type="WhereSwitchType" substitutionGroup="LESS:switch"/
      <xs:complexType name="WhereType"
        <xs:group ref="LESS:Node"/
        <xs:attribute name="changed" type="xs:boolean" default="true"/
        <xs:attribute name="longitude" type="xs:string"
          <xs:annotation
            <xs:documentationValid only if type is geospatial</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="latitude" type="xs:string"
          <xs:annotation
            <xs:documentationValid only if type is geospatial</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="altitude" type="xs:string"
          <xs:annotation
            <xs:documentationValid only if type is geospatial</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="A1" type="xs:string"
          <xs:annotation
            <xs:documentationValid only if type is civil</xs:documentation
          </xs:annotation
        </xs:attribute



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        <xs:attribute name="A2" type="xs:string"
          <xs:annotation
            <xs:documentationValid only if type is civil</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="A3" type="xs:string"
          <xs:annotation
            <xs:documentationValid only if type is civil</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="A4" type="xs:string"
          <xs:annotation
            <xs:documentationValid only if type is civil</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="A5" type="xs:string"
          <xs:annotation
            <xs:documentationValid only if type is civil</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="A6" type="xs:string"
          <xs:annotation
            <xs:documentationValid only if type is civil</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="PRD" type="xs:string"
          <xs:annotation
            <xs:documentationValid only if type is civil</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="POD" type="xs:string"
          <xs:annotation
            <xs:documentationValid only if type is civil</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="STS" type="xs:string"
          <xs:annotation
            <xs:documentationValid only if type is civil</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="HNO" type="xs:string"
          <xs:annotation
            <xs:documentationValid only if type is civil</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="HNS" type="xs:string"
          <xs:annotation
            <xs:documentationValid only if type is civil</xs:documentation



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          </xs:annotation
        </xs:attribute
        <xs:attribute name="LMK" type="xs:string"
          <xs:annotation
            <xs:documentationValid only if type is civil</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="LOC" type="xs:string"
          <xs:annotation
            <xs:documentationValid only if type is civil</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="FLR" type="xs:string"
          <xs:annotation
            <xs:documentationValid only if type is civil</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="NAM" type="xs:string"
          <xs:annotation
            <xs:documentationValid only if type is civil</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="PC" type="xs:string"
          <xs:annotation
            <xs:documentationValid only if type is civil</xs:documentation
          </xs:annotation
        </xs:attribute
        <xs:attribute name="distance"
          <xs:annotation
            <xs:documentationValid only if geospatial or civil location presented</xs:documentation
          </xs:annotation
          <xs:simpleType
            <xs:restriction base="xs:decimal"
              <xs:minInclusive value="0"/
            </xs:restriction
          </xs:simpleType
        </xs:attribute
        <xs:attribute name="condition" default="at"
          <xs:annotation
            <xs:documentationValid only if distance presented</xs:documentation
          </xs:annotation
          <xs:simpleType
            <xs:restriction base="xs:string"
              <xs:enumeration value="in"/
              <xs:enumeration value="out"/
              <xs:enumeration value="at"/
            </xs:restriction
          </xs:simpleType



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        </xs:attribute
        <xs:attribute name="unit" default="m"
          <xs:annotation
            <xs:documentationValid only if distance presented</xs:documentation
          </xs:annotation
          <xs:simpleType
            <xs:restriction base="xs:string"
              <xs:enumeration value="m"/
              <xs:enumeration value="km"/
              <xs:enumeration value="mi"/
              <xs:enumeration value="in"/
              <xs:enumeration value="ft"/
              <xs:enumeration value="yd"/
              <xs:enumeration value="naut mi"/
            </xs:restriction
          </xs:simpleType
        </xs:attribute
        <xs:attribute name="direction"
          <xs:annotation
            <xs:documentationValid only if geospatial or civil location presented</xs:documentation
          </xs:annotation
          <xs:simpleType
            <xs:restriction base="xs:string"
              <xs:enumeration value="south"/
              <xs:enumeration value="north"/
              <xs:enumeration value="east"/
              <xs:enumeration value="west"/
              <xs:enumeration value="above"/
              <xs:enumeration value="below"/
            </xs:restriction
          </xs:simpleType
        </xs:attribute
        <xs:anyAttribute namespace="##other" processContents="lax"/
      </xs:complexType
      <xs:complexType name="WhereRelationSwitchType"
        <xs:sequence
          <xs:element name="where-relation" type="WhereRelationType" minOccurs="0" maxOccurs="unbounded"/
          <xs:sequence minOccurs="0"
            <xs:element name="not-present" type="LESS:NotPresentAction"/
            <xs:element name="where-relation" type="WhereRelationType" minOccurs="0" maxOccurs="unbounded"/
          </xs:sequence
          <xs:element name="otherwise" type="LESS:OtherwiseAction" minOccurs="0"/
        </xs:sequence
        <xs:attribute name="uri1" type="xs:anyURI" use="required"/
        <xs:attribute name="uri2" type="xs:anyURI"/
      </xs:complexType
      <xs:element name="where-relation-switch" type="WhereRelationSwitchType" substitutionGroup="LESS:switch"/
      <xs:simpleType name="WhereAttributes"



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        <xs:restriction base="xs:string"
          <xs:enumeration value="latitude"/
          <xs:enumeration value="longitude"/
          <xs:enumeration value="altitude"/
          <xs:enumeration value="country"/
          <xs:enumeration value="A1"/
          <xs:enumeration value="A2"/
          <xs:enumeration value="A3"/
          <xs:enumeration value="A4"/
          <xs:enumeration value="A5"/
          <xs:enumeration value="A6"/
          <xs:enumeration value="PRD"/
          <xs:enumeration value="POD"/
          <xs:enumeration value="STS"/
          <xs:enumeration value="HNO"/
          <xs:enumeration value="HNS"/
          <xs:enumeration value="LMK"/
          <xs:enumeration value="LOC"/
          <xs:enumeration value="FLR"/
          <xs:enumeration value="NAM"/
          <xs:enumeration value="PC"/
        </xs:restriction
      </xs:simpleType
      <xs:complexType name="WhereRelationType"
        <xs:group ref="LESS:Node"/
        <xs:attribute name="distance"
          <xs:annotation
            <xs:documentationValid only if geospatial or civil location presented</xs:documentation
          </xs:annotation
          <xs:simpleType
            <xs:restriction base="xs:decimal"
              <xs:minInclusive value="0"/
            </xs:restriction
          </xs:simpleType
        </xs:attribute
        <xs:attribute name="condition" default="at"
          <xs:annotation
            <xs:documentationValid only if distance presented</xs:documentation
          </xs:annotation
          <xs:simpleType
            <xs:restriction base="xs:string"
              <xs:enumeration value="in"/
              <xs:enumeration value="out"/
              <xs:enumeration value="at"/
            </xs:restriction
          </xs:simpleType
        </xs:attribute
        <xs:attribute name="unit" default="m"



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          <xs:annotation
            <xs:documentationValid only if distance presented</xs:documentation
          </xs:annotation
          <xs:simpleType
            <xs:restriction base="xs:string"
              <xs:enumeration value="m"/
              <xs:enumeration value="km"/
              <xs:enumeration value="mi"/
              <xs:enumeration value="in"/
              <xs:enumeration value="ft"/
              <xs:enumeration value="yd"/
              <xs:enumeration value="naut mi"/
            </xs:restriction
          </xs:simpleType
        </xs:attribute
        <xs:attribute name="direction"
          <xs:annotation
            <xs:documentationValid only if geospatial or civil location presented</xs:documentation
          </xs:annotation
          <xs:simpleType
            <xs:restriction base="xs:string"
              <xs:enumeration value="south"/
              <xs:enumeration value="north"/
              <xs:enumeration value="east"/
              <xs:enumeration value="west"/
              <xs:enumeration value="above"/
              <xs:enumeration value="below"/
            </xs:restriction
          </xs:simpleType
        </xs:attribute
        <xs:attribute name="same"
          <xs:simpleType
            <xs:list itemType="WhereAttributes"/
          </xs:simpleType
        </xs:attribute
        <xs:attribute name="difference"
          <xs:simpleType
            <xs:list itemType="WhereAttributes"/
          </xs:simpleType
        </xs:attribute
        <xs:anyAttribute namespace="##other" processContents="lax"/
      </xs:complexType
    </xs:schema


 19.8 XML Schema for LESS Queue Handling Extension





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    <?xml version="1.0" encoding="UTF-8"?
    <!-- edited with XMLSPY v2004 rel. 2 U (http://www.xmlspy.com) by Xiaotao Wu (Columbia University Computer Science Dept) --
    <xs:schema targetNamespace="urn:ietf:params:xml:ns:less:queue" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:LESS="urn:ietf:params:xml:ns:less" xmlns="urn:ietf:params:xml:ns:less:queue" elementFormDefault="qualified" attributeFormDefault="unqualified"
      <xs:import namespace="urn:ietf:params:xml:ns:less" schemaLocation="less.xsd"/
      <xs:simpleType name="QueueName"
        <xs:union
          <xs:simpleType
            <xs:restriction base="xs:NMTOKEN"
              <xs:enumeration value="callback"/
              <xs:enumeration value="hold"/
            </xs:restriction
          </xs:simpleType
          <xs:simpleType
            <xs:restriction base="xs:string"/
          </xs:simpleType
        </xs:union
      </xs:simpleType
      <xs:complexType name="EnqueueActionType"
        <xs:complexContent
          <xs:extension base="LESS:ActionType"
            <xs:all
              <xs:element name="full" minOccurs="0"
                <xs:complexType
                  <xs:group ref="Node"/
                </xs:complexType
              </xs:element
            </xs:all
            <xs:attribute name="queue" type="QueueName" use="optional"/
            <xs:attribute name="maxlen" type="xs:positiveInteger" use="optional"/
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="enqueue" type="EnqueueActionType" substitutionGroup="LESS:action"/
      <xs:complexType name="DequeueActionType"
        <xs:complexContent
          <xs:extension base="LESS:ActionType"
            <xs:all
              <xs:element name="success" minOccurs="0"
                <xs:complexType
                  <xs:group ref="Node"/
                </xs:complexType
              </xs:element
              <xs:element name="failure" minOccurs="0"
                <xs:complexType
                  <xs:group ref="Node"/
                </xs:complexType
              </xs:element



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            </xs:all
            <xs:attribute name="queue" type="QueueName" use="optional"/
          </xs:extension
        </xs:complexContent
      </xs:complexType
      <xs:element name="dequeue" type="DequeueActionType" substitutionGroup="LESS:action"/
    </xs:schema


 20 References

 20.1 Normative References

    [1] S. Bradner, "Key words for use in RFCs to indicate requirement
    levels," RFC 2119, Internet Engineering Task Force, Mar. 1997.

    [2] J. Lennox, X. Wu, and H. Schulzrinne, "Call processing language
    (CPL): a language for user control of Internet telephony services,"
    rfc, Internet Engineering Task Force, Oct. 2004.  Standard.

    [3] T. Bray, J. Paoli, and C. M. Sperberg-McQueen, "Extensible markup
    language (XML) 1.0 (second edition)," W3C Recommendation REC-xml-
    20001006, World Wide Web Consortium (W3C), Oct. 2000.  Available at
    http://www.w3.org/XML/.

    [4] D. C. Fallside, "XML schema part 0: Primer," W3C Candidate
    Recommendation CR-xmlschema-0-20001024, World Wide Web Consortium
    (W3C), Oct. 2000.  Available at http://www.w3.org/TR/xmlschema-0/.

    [5] H. Schulzrinne, "RPID -- rich presence information data format,"
    Internet Draft draft-ietf-simple-rpid-01, Internet Engineering Task
    Force, Feb. 2004.  Work in progress.

    [6] R. Moats, "URN syntax," RFC 2141, Internet Engineering Task
    Force, May 1997.

    [7] R. Moats, "A URN namespace for IETF documents," RFC 2648,
    Internet Engineering Task Force, Aug. 1999.

    [8] R. Mahy, "The ietf xml registry," RFC 3688, Internet Engineering
    Task Force, Jan. 2004.

    [9] M. Murata, S. S. Laurent, and D. Kohn, "XML media types," RFC
    3023, Internet Engineering Task Force, Jan. 2001.

    [10] T. Bray, D. Hollander, and A. Layman, "Namespaces in XML," W3C
    Recommendation REC-xml-names-19900114, World Wide Web Consortium
    (W3C), Jan. 1999.  Available at http://www.w3.org/TR/REC-xml-names/.



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 20.2 Informative References

    [11] X. Wu and H. Schulzrinne, "Where should services reside in
    Internet telephony systems?," in IP Telecom Services Workshop,
    (Atlanta, Georgia), Sept. 2000.

    [12] X. Wu and H. Schulzrinne, "Programmable end system services
    using SIP," in Conference Record of the International Conference on
    Communications (ICC), May 2003.

    [13] R. Stansifer, Study of Programming Languages, vol. 1.  Florida
    Institute of Technology: Prentice Hall, 1994.

    [14] A. D. Falkoff and K. E. Iverson, "The design of APL," SIGAPL APL
    Quote Quad, vol. 6, no. 1, pp. 5--14, 1975.

    [15] X. Wu and H. Schulzrinne, "Feature interactions in Internet
    telephony end systems," tech. rep., Department of Computer Science,
    Columbia University, Jan. 2004.

    [16] International Telecommunication Union, "General recommendations
    on telephone switching and signaling -- intelligent network:
    Introduction to intelligent network capability set 1," Recommendation
    Q.1211, International Telecommunication Union, Geneva, Switzerland,
    Mar. 1993.

    [17] AT&T, 5ESS Switch, The Premier Solution, Feature Handbook, Issue
    4.  AT&T, Sept. 1987.

    [18] E. International, "Services for computer supported
    telecommunications applications (CSTA) Phase III," Standard 269, Ecma
    International, June 2004.

    [19] J. Lennox, H. Schulzrinne, and T. L. Porta, "Implementing
    intelligent network services with the session initiation protocol,"
    Technical Report CUCS-002-99, Columbia University, New York, New
    York, Jan. 1999.

    [20] VoiceXML Forum, "Voicexml home page." http://www.voicexml.org/.

    [21] R. Mahy, "A message summary and message waiting indication event
    package for the session initiation protocol (SIP)," RFC 3842,
    Internet Engineering Task Force, Aug. 2004.

 Authors' Addresses

    Xiaotao Wu
    Dept. of Computer Science



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    Columbia University
    1214 Amsterdam Avenue, MC 0401
    New York, NY 10027
    USA
    electronic mail: xiaotaow@cs.columbia.edu

    Henning Schulzrinne
    Dept. of Computer Science
    Columbia University
    1214 Amsterdam Avenue, MC 0401
    New York, NY 10027
    USA
    electronic mail: schulzrinne@cs.columbia.edu






































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