Network Working Group H. Sugano INTERNET-DRAFT S. Fujimoto Fujitsu G. Klyne Baltimore Technologies A. Bateman VisionTech W. Carr Intel Expires: November 2002 May 2002 CPIM Presence Information Data Format Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet- Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Please send comments to the authors or to the impp@iastate.edu discussion list. Copyright Notice Copyright (C) The Internet Society (2002). All Rights Reserved. Abstract This memo specifies the CPIM Presence Information Data Format (PIDF) as a common presence data format for CPIM-compliant IM/Presence protocols, and also defines a new media type "application/cpim- pidf+xml" to represent the XML MIME entity for PIDF. Sugano et al. [Page 1] INTERNET DRAFT CPIM Presence Format May 2002 Table of Content 1. Introduction ......................................... 3 1.1. Terminology and Conventions .......................... 3 2. Design Decisions ..................................... 4 2.1. Minimal Model ........................................ 4 2.2. Added Features ....................................... 5 2.3. XML Encoding Decision ................................ 5 3. Overview of Presence Information Data Format ......... 5 3.1. The 'application/cpim-pidf+xml' Content Type ......... 6 3.2. Presence Information Contents ........................ 6 4. XML-encoded Presence Data Format ..................... 6 4.1. XML Format Definitions ............................... 6 4.1.1. The element ............................... 7 4.1.2. The element .................................. 7 4.1.3. The element ................................. 8 4.1.4. The element .................................. 8 4.1.5. The element ................................ 8 4.1.6. The element ................................... 9 4.1.7. The element .............................. 9 4.2. Presence Information Extensibility ................... 9 4.2.1. XML Namespaces Background ............................ 9 4.2.2. XML Namespaces In Presence Information ............... 10 4.2.3. Handling Of Unrecognized Element Names ............... 11 4.2.4. Status Value Extensibility ........................... 12 4.3. Examples ............................................. 12 4.3.1. Default Namespace with Status Extensions ............. 12 4.3.2. Presence with Other Extension Elements ............... 13 4.3.3. Example Mandatory To Understand Extensions ........... 13 4.4. XML Schema Definitions ............................... 14 5. IANA Considerations .................................. 16 5.1. Content-type registration for 'application/cpim-pidf+xml' .................................................... 16 5.2. URN sub-namespace registration for 'urn:ietf:params:xml:ns:cpim-pidf' ................. 17 6. Security Considerations .............................. 18 7. Internationalization Considerations .................. 18 8. References ........................................... 19 9. Authors' Addresses ................................... 20 10. Appendix A. Document Type Definitions ............... 21 11. Full Copyright Statement ............................ 22 Sugano et al. [Page 2] INTERNET DRAFT CPIM Presence Format May 2002 1. Introduction The Common Profile for Instant Messaging (CPIM) specifications define a set of common operations and various formats to achieve interoperability between different Instant Messaging and Presence protocols which meet RFC 2779 [RFC2779]. The CPIM core specification [CPIM] defines a set of common operations and their parameters to be supported by interworking Presence and IM protocols in order to allow straightforward gatewaying between them. The work on CPIM Message Format [CPIM-MSG] defines a common format for instant messages, which enables secure end-to-end IM exchange through the gateways. This memo further defines the CPIM Presence Information Data Format (PIDF) as a common presence data format for CPIM-compliant presence protocols. The significance of the common presence format primarily resides in the fact that it alleviates the load of gatewaying of messages with presence data payloads. Without such a common presence data format, a gateway must process and transform the presence data payload from one format to another every time it gateways the protocol messages. Such payload processing also disables the validity of digitally signed presence data. Utilizing the common presence data format allows secure transfer of the presence payloads across the boundary of different protocol domains. The format specified in this memo is intended to define the base presence format and extensibility required by RFC 2779. It only defines a minimal set of presence status values defined by the IMPP Model document [RFC2778]. However, a presence application is able to define its own status values using the extensibility framework provided by this memo. Defining such extended status values is beyond the scope of this memo. Note also that this memo only defines the format for a presence data payload only and how the presence data is transferred within a specific protocol frame would be defined in actual protocol specifications. 1.1. Terminology and Conventions This memo makes use of the vocabulary defined in the IMPP Model document [RFC2778]. Terms such as CLOSED, INSTANT MESSAGE, OPEN, PRESENCE SERVICE, PRESENTITY, WATCHER, and WATCHER USER AGENT in the memo are used in the same meaning as defined therein. The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. Sugano et al. [Page 3] INTERNET DRAFT CPIM Presence Format May 2002 [[[Editorial comments and questions about outstanding issues are provided in triple brackets like this. These working comments should be resolved and removed prior to final publication.]]] 2. Design Decisions We have adopted the IMPP Model and Requirements documents [RFC2778, RFC2779] as the starting point of our discussion. The two RFCs contains a number of statements about presence information, which can be regarded as a basic set of constraints for the format design. Also, we took the minimalist approach to the design based on them. Starting from the minimal model, only the features that are necessary to solve particular problems have been combined. 2.1. Minimal Model This specification is based on the minimal model extracted from the IMPP Model and Requirements documents. The model consists of the following items. Each of them is accompanied with the corresponding RFCs and their section numbers as its grounds, e.g. (RFC2778:Sec.2.4) refers to Section 2.4 of RFC 2778. (a) PRESENCE INFORMATION consists of one or more PRESENCE TUPLES, where a PRESENCE TUPLE consists of a STATUS, an optional COMMUNICATION ADDRESS, and optional OTHER PRESENCE MARKUP. (RFC2778:Sec.3) (b) STATUS has at least the mutually-exclusive values OPEN and CLOSED, which have meaning for the acceptance of INSTANT MESSAGES, and may have meaning for other COMMUNICATION MEANS. There may be other values of STATUS that do not imply anything about INSTANT MESSAGE acceptance. These other values of STATUS may be combined with OPEN and CLOSED or they may be mutually- exclusive with those values. (RFC2778:Sec.3, RFC2779:Sec.4.4.1- 4.4.3) (c) STATUS may consist of single or multiple values. (RFC2778:Sec.2.4) (d) There must be a means of extending the common presence format to represent additional information not included in the common format. The extension and registration mechanisms must be defined for presence information schema, including new STATUS conditions and new forms for OTHER PRESENCE MARKUP. (RFC2779: Sec.3.1.4-3.1.5) (e) The common presence format must include a means to uniquely Sugano et al. [Page 4] INTERNET DRAFT CPIM Presence Format May 2002 identify the PRESENTITY whose PRESENCE INFORMATION is reported. (RFC2779:Sec.3.1.2) (f) The common presence format must allow the source of the presence data (i.e. PRESENTITY) to utilize some security mechanism (e.g. digital signature or encryption) for the secure transportation of the data. (RFC2779:Sec.5.2.1, 5.3.1, 5.3.3) (g) The common presence format must be extensible to represent additional information not defined in this memo. (RFC2779: Sec.3.1.4) 2.2. Added Features In addition to the minimal model described above, the format specified in this specification has the following features. (a) Relative priorities of contact addresses should be specifiable in order to allow the source of PRESENCE INFORMATION to tell the receiver (WATCHER USER AGENTS) its preference over multiple contact means. (b) The presence format should be able to contain the timestamp of the creation of the PRESENCE INFORMATION. The timestamp in the presence document lets the receiver know the time of the creation of the data even if the message containing it arrives late for some reason. It can also be used to detect a replay attack, independent of the underlying signature mechanism. 2.3. XML Encoding Decision The CPIM Presence Information Data Format encodes presence information in XML (eXtensible Markup Language [XML]), which is rapidly gaining broad acceptance as a syntactic framework to encode structured data transferred over the Internet. Regarding the features of PRESENCE INFORMATION discussed above, such that it has a hierarchical structure and it should be fully extensible, XML is considered as the most desirable framework over other candidates such as vCard [RFC2426]. 3. Overview of Presence Information Data Format This section describes an overview of the presence data format defined in this memo. Sugano et al. [Page 5] INTERNET DRAFT CPIM Presence Format May 2002 3.1. The 'application/cpim-pidf+xml' Content Type This memo defines a new content type "application/cpim-pidf+xml" to represent an XML MIME entity which encodes a presence information document conformant to this specification. Because the new content type is XML-based, this specification follows the recommendations and conventions described in [RFC3023], including the naming convention of the type ('+xml' suffix) and the usage of the 'charset' parameter. As for the 'charset' parameter, although it is defined as optional, the use of that parameter is STRONGLY RECOMMENDED. If the 'charset' parameter is not specified, conforming XML processors to [XML] MUST follow the requirements in section 4.3.3 of [XML]. 3.2. Presence Information Contents This subsection outlines types of information included in an "application/cpim-pidf+xml" type document. The real definition of the content type will be presented in Section 4. o PRESENTITY URL: specifies the "pres" URL of the PRESENTITY. o List of presence tuples - Status: OPEN/CLOSED for Instant Messaging or status for other communication means. - Communication address: communication means and contact address of this tuple. (optional) - Relative priority: numerical value specifying the priority of this communication address. (optional) - Timestamp: timestamp of the change of this tuple.(optional) - Human readable comment: free text memo about this tuple (optional) o PRESENTITY human readable comment: free text memo about the PRESENTITY (optional). 4. XML-encoded Presence Data Format This section defines an XML-encoded presence data format of the content type "application/cpim-pidf+xml" for presence payloads. A presence payload of this type is expected to be produced by the PRESENTITY (the source of the PRESENCE INFORMATION) and transported to the WATCHERS by the presence servers or gateways without any interpretation or modification. 4.1. XML Format Definitions Sugano et al. [Page 6] INTERNET DRAFT CPIM Presence Format May 2002 An "application/cpim-pidf+xml" object is a well formed XML document. It MUST have the XML declaration and it SHOULD contain an encoding declaration in the XML declaration, e.g. "". If the charset parameter of the MIME content type declaration is present and it is different from the encoding declaration, the charset parameter takes precedence. 4.1.1. The element The root element of the "application/cpim-pidf+xml" object is defined as . This element contains one or more elements, followed by any number (including 0) of OPTIONAL elements, followed by any number of OPTIONAL extension elements from other namespaces. The element MUST have an 'entity' attribute. The value of the 'entity' attribute is the 'pres' URL of the PRESENTITY publishing this presence document. The element MUST contain a namespace declaration ('xmlns') to indicate the namespace on which the presence document is based. The presence document compliant to this specification MUST have the namespace 'urn:ietf:params:xml:ns:cpim-pidf:'. It MAY contain other namespace declarations for the extensions used in the presence XML document. 4.1.2. The element The element is used to carry a piece of PRESENCE INFORMATION defined as PRESENCE TUPLE in RFC2778. Thus, it contains one mandatory element, followed by any number of OPTIONAL extension elements from other namespaces, followed by one OPTIONAL elements, followed by any number of OPTIONAL elements, followed by one OPTIONAL elements. The element MUST contain an 'id' attribute which is used to distinguish this tuple from other tuples in the same XML document. The value of an 'id' attribute MUST be unique within 'id' attribute values of other tuples in the same document. An 'id' value is used by applications processing the presence document to identify the corresponding tuple in the previously acquired PRESENCE INFORMATION of the same PRESENTITY. The value of the 'id' attribute SHOULD be treated as just a CDATA value (no semantics). Sugano et al. [Page 7] INTERNET DRAFT CPIM Presence Format May 2002 The element is OPTIONAL because a PRESENTITY might need to hide its communication address or there might be tuples not related to any communication means. 4.1.3. The element The element contains one OPTIONAL elements, followed by any number of OPTIONAL extension elements from other namespaces, under the restriction that at least one child element appears in the element. These children elements of contain status values of this tuple. By allowing multiple status values in a single element, different types of status values, e.g. reachability and location, can be represented by a . See Section 4.3 for an example with multiple status values. This memo only defines the status value element. Other status values may be included using the standard extensibility framework (see Section 4.2.4). Applications encountering unrecognized elements within may ignore them, unless they carry a mustUnderstand="true" or mustUnderstand="1" attribute (see section 4.2.3). Note that, while the element MUST have at least one status value element, this status value may not be the element. 4.1.4. The element The element contains one of the following strings: "open" or "closed". The values "open" and "closed" has the same meaning as OPEN and CLOSED defined in RFC 2778 respectively, and stand for availability of receiving instant messages if the is for an instant messaging address. They also have meanings of general availability for other communication means. But, this memo does not specify them in detail. 4.1.5. The element The element contains a URL of the contact address. It optionally has a 'priority' attribute, whose value means a relative priority of this contact address over the others. The value of the attribute MUST be a decimal number between 0 and 1 inclusive with at most 3 digits after the decimal point. Higher values indicate higher priority. Examples of priority values are 0, 0.021, 0.5, 1.00. If the 'priority' attribute is omitted, applications MUST understand that the contact address has the lowest priority. If the 'priority' value Sugano et al. [Page 8] INTERNET DRAFT CPIM Presence Format May 2002 is out of the range, applications just SHOULD ignore the value and process it as if the attribute was not present. It is RECOMMENDED that applications handles a tuple with higher priority than another one so that the priority is recognizable by users. How to handle tuples with the same priority is up to implementations. 4.1.6. The element The element contains a string value, which is usually used for a human readable comment. A element MAY appear as a child element of or as a child element of the element. In the former case, the comment is about the PRESENTITY and, in the latter case, the comment is regarding the particular tuple. The element SHOULD have a special attribute 'xml:lang' to specify the language used in the contents of this element as defined in Section 2.12 of [XML]. The value of this attribute is the language indentifier as defined by [RFC 1766]. It MAY be omitted when the language used is implied by the larger context such as the encoding information of the contents, e.g. the 'Shift_JIS' encoding imples the language 'ja'. 4.1.7. The element The element contains a string indicating the date and time of the status change of this tuple. The value of this element MUST follow the IMPP datetime format [DateTime]. While the IMPP datetime format allows use of either 'z' or 'Z' and also 't' or 'T', XML Schema's dateTime requires using only 'T' and 'Z'. Timestamps that contain 'T' or 'Z' MUST use the capitalized forms [XMLSchema2]. 4.2. Presence Information Extensibility The presence information extensibility framework is based on XML namespaces [XML-NS]. 4.2.1. XML Namespaces Background All elements and some attributes are associated with a "namespace", which is in turn associated with a globally unique URI. Any Sugano et al. [Page 9] INTERNET DRAFT CPIM Presence Format May 2002 developer can introduce their own element names, avoiding conflict by choosing an appropriate namespace URI. Within the presence data, element or attribute names are associated with a particular namespace by a namespace prefix, which is a leading part of the name, followed by a colon (":"); e.g. ... Where, 'prefix' is the header name prefix, 'element-name' is a name which is scoped by the namespace associated with 'prefix'. Note that the choice of 'prefix' is quite arbitrary; it is the corresponding URI that defines the naming scope. Two different prefixes associated with the same namespace URI refer to the same namespace. A default namespace can be declared for XML elements without a namespace prefix. The default namespace does NOT apply to attribute names, but interpretation of an unprefixed attribute can be determined by the containing element. A namespace is identified by a URI. In this usage, the URI is used simply as a globally unique identifier, and there is no requirement that it can be used to retrieve a web resource, or for any other purpose. Any legal globally unique URI MAY be used to identify a namespace. (By "globally unique", we mean constructed according to some set of rules so that it is reasonable to expect that nobody else will use the same URI for a different purpose.) For further details, see the XML namespace specification [XML-NS]. 4.2.2. XML Namespaces In Presence Information A URI used as a namespace identifier in PRESENCE INFORMATION data MUST be a full absolute-URI, per RFC 2396 [URI]. (Relative URIs and URI- references containing fragment identifiers MUST NOT be used for this purpose.) The namespace URI for elements defined by this specification is a URN [URN], using the namespace identifier 'ietf' defined by [URN-NS-IETF] and extended by [URN-Registry]: urn:ietf:params:xml:ns:cpim-pidf Thus, simple presence data might be thus: open tel:09012345678 or, using a default XML namespace: open tel:09012345678 As is generally the case in XML, the xmlns attribute can be used on any element in the presence information to define either the default namespace or a namespace associated with a namespace prefix. 4.2.3. Handling Of Unrecognized Element Names Except as noted below, a processor of PRESENCE INFORMATION MUST ignore any XML element with an unrecognized name (i.e. having an unrecognized namespace URI, or an unrecognized local name within that namespace). This includes all of the element content, even if it appears to use recognized names. It may be that some extensions must be understood in order for the presence information to be properly understood. In such cases, the element name is qualified with a mustUnderstand='true' or mustUnderstand='1' attribute, which attribute name is associated with the CPIM presence namespace. NOTE: a mustUnderstand='true' or mustUnderstand='1' attribute within an element that is being ignored is itself ignored. The writer of nested mandatory-to-understand information is responsible for ensuring that any enclosing element is also labelled with a mustUnderstand='true' or mustUnderstand='1' attribute, if necessary. Sugano et al. [Page 11] INTERNET DRAFT CPIM Presence Format May 2002 This specification defines (section 4.1) elements within the 'urn:ietf:params:xml:ns:cpim-pidf' namespace that MUST be recognized in CPIM presence data. Processors MUST handle these as described, even if they do not carry a mustUnderstand attribute. The XML Schema Definition (section 4.4) indicates those elements that MUST be present in a valid presence information document. If an agent receives PRESENCE INFORMATION containing an unrecognized element with a mustUnderstand='true' (or '1') attribute, it should treat the entire PRESENCE INFORMATION as unrecognized and not attempt to process it. 4.2.4. Status Value Extensibility This memo only defines the status value with values of "open" and "closed". Other status values are possible using the standard namespace-based extensibility rules defined above. For example, a location status value might be included thus: open home im:someone@example.com Some new status values will 'extend' the value of the element. For example, a status value defined for use with instant messaging may include values such as 'away', 'busy' and 'offline'. In order that some level of interoperability be maintained with user agents that don't recognise the new extension, the status value must also be included. This means that extensions are not obligated to define a mapping from each of their values to OPEN or CLOSED. 4.3. Examples 4.3.1. Default Namespace with Status Extensions Sugano et al. [Page 12] INTERNET DRAFT CPIM Presence Format May 2002 open busy home im:someone@mobilecarrier.net Don't Disturb Please! Ne derangez pas, s'il vous plait 2001-10-27T16:49:29Z open mailto:someone@example.com I'll be in Tokyo next week 4.3.2. Presence with Other Extension Elements open Extended value in tuple tel:09012345678 open im:someone@mobilecarrier.net My extended presentity information Sugano et al. [Page 13] INTERNET DRAFT CPIM Presence Format May 2002 4.3.3. Example Mandatory To Understand Extensions open val1 val2 tel:09012345678 My extended presentity information Here, , must be understood, but and may be ignored if they are not recognized. 4.4. XML Schema Definitions This section gives the XML Schema Definition [XMLSchema1] of the "application/cpim-pidf+xml" format. This is presented as a formal definition of the "application/cpim-pidf+xml" format. Note that the XML Schema definition is not intended to be used with on-the-fly validation of the presence XML document. Sugano et al. [Page 15] INTERNET DRAFT CPIM Presence Format May 2002 5. IANA Considerations This memo calls for IANA to: - register a new MIME content-type application/cpim-pidf+xml, per [RFC 2048], - register a new XML namespace URN per [XML-Registry]. The registration templates for these are below. 5.1. Content-type registration for 'application/cpim-pidf+xml' To: ietf-types@iana.org Subject: Registration of MIME media type application/cpim-pidf+xml MIME media type name: application MIME subtype name: cpim-pidf+xml Required parameters: (none) Optional parameters: charset Indicates the character encoding of enclosed XML. Default is UTF-8. Encoding considerations: Uses XML, which can employ 8-bit characters, depending on the character encoding used. See RFC 3023 [RFC 3023], section 3.2. Security considerations: Sugano et al. [Page 16] INTERNET DRAFT CPIM Presence Format May 2002 This content type is designed to carry presence data, which may be considered private information. Appropriate precautions should be adopted to limit disclosure of this information. Interoperability considerations: This content type provides a common format for exchange of presence information across different CPIM compliant protocols. Published specification: RFCXXXX (this document) Applications which use this media type: Presence and instant messaging systems. Additional information: Magic number(s): File extension(s): Macintosh File Type Code(s): Person & email address to contact for further information: Hiroyasu Sugano E-mail: sugano.h@jp.fujitsu.com Intended usage: LIMITED USE Author/Change controller: This specification is a work item of the IETF IMPP working group, with mailing list address . Other information: This media type is a specialization of application/xml [RFC 3023], and many of the considerations described there also apply to application/cpim-pidf+xml. 5.2. URN sub-namespace registration for 'urn:ietf:params:xml:ns:cpim- pidf' URI urn:ietf:params:xml:ns:cpim-pidf Description: This is the XML namespace URI for XML elements defined by [RFCXXXX] to describe CPIM presence information in application/cpim-pidf+xml content type. Sugano et al. [Page 17] INTERNET DRAFT CPIM Presence Format May 2002 Registrant Contact IETF, IMPP working group, Hiroyasu Sugano, XML BEGIN Welcome to Adobe GoLive 6

Namespace for CPIM presence information

application/cpim-pidf+xml

See RFCXXXX.

END 6. Security Considerations Because presence is very privacy-sensitive information, the transport protocol for the presence information SHOULD have capabilities to protect protocol messages from possible threats, such as eavesdropping, corruption, tamper and replay attacks. The protocols SHOULD be able to use security mechanisms which are standardized or being standardized in IETF. However, it depends on the actual transport protocols which security mechanisms should be used, and it is beyond the scope of this memo. 7. Internationalization Considerations This memo does not specify the use of specific character encodings by itself. However, all the processors MUST be able to use the UTF-8 encoding because it is one of the mandatory character encodings for XML conforming processors and also RFC 2277 requires the handling of UTF-8 for the Internet protocols [RFC2277]. Other character encodings may be used if a particular protocol or application using this specification needs them. In this case, a conscious decision is needed about which character encoding(s) to Sugano et al. [Page 18] INTERNET DRAFT CPIM Presence Format May 2002 allow in order to promote the interoperability. 8. References [CPIM] D. Crocker et al., "A Common Profile for Instant Messaging (CPIM)", draft-ietf-impp-cpim-02.txt, Work in Progress. [CPIM-MSG] D. Atkins and G. Klyne, "Common Presence and Instant Messaging Message Format", draft-ietf-impp-cpim-msgfmt-06.txt, Work in Progress. [RFC2119] S. Bradner, "Key words for use in RFCs to Indicate Requirement Levels", RFC 2119, BCP 14, March 1997. [RFC2778] M. Day, J. Rosenberg, H. Sugano, "A Model for Presence and Instant Messaging", RFC 2778, February 2000. [RFC2779] M. Day, S. Aggarwal, G. Mohr, and J. Vincent, "Instant Messaging / Presence Protocol Requirements", RFC 2779, February 2000. [vCard] F. Dawson and T. Howes, "vCard MIME Directory Profile", RFC 2426, September 1998. [RFC3023] M. Murata, S. St.Laurent, D. Kohn, "XML Media Types", RFC 3023, January 2001. [XML] T. Bray, J. Paoli, C. Sperberg-McQueen and E. Maler, "Extensible Markup Language (XML) 1.0 (Second Edition)", W3C Recommendation, October 2000, [MIME] Multipurpose Internet Mail Extensions. See RFC 822, RFC 2045, RFC 2046, RFC 2047, RFC 2048, and RFC 2049. [RFC1766] H. Alvestrand, "Tags for the identification of languages", RFC 1766, March 1995. [DateTime] G. Klyne and C.Newman, "Date and Time on the Internet: Timestamps", draft-ietf-impp-datetime-05.txt, Work in Progress. [XML-NS] Tim Bray, Dave Hollander, and Andrew Layman "Namespaces in XML", W3C recommendation: xml-names, 14 January 1999, [URI] T. Berners-Lee, R.T.Fielding and L. Masinter, "Uniform Resource Identifiers (URI): Generic Syntax", RFC 2396, August 1998. Sugano et al. [Page 19] INTERNET DRAFT CPIM Presence Format May 2002 [URN] R. Moats, "URN Syntax", RFC 2141, May 1997. [URN-NS-IETF] R. Moats, "A URN Namespace for IETF Documents", RFC 2648, August 1999. [XML-Registry] M. Mealling, "The IETF XML Registry", draft-mealling-iana-xmlns-registry-03, Work in Progress. [RFC2277] H. Alvestrand, "IETF Policy on Character Sets and Languages", RFC 2277, BCP 18, January 1998. [XMLSchema1] Thompson, H., Beech, D., Maloney, M. and N. Mendelsohn, "XML Schema Part 1: Structures", W3C REC-xmlschema-1, May 2001, . [XMLSchema2] Biron, P. and A. Malhotra, "XML Schema Part 2: Datatypes", W3C REC-xmlschema-2, May 2001, . 9. Authors' Addresses Hiroyasu Sugano Fujitsu Laboratories Ltd. 64, Nishiwaki Ohkubo-cho Akashi 674-8555 Japan E-mail: sugano.h@jp.fujitsu.com Shingo Fujimoto Fujitsu Laboratories Ltd. 64, Nishiwaki Ohkubo-cho Akashi 674-8555 Japan E-mail: shingo_fujimoto@jp.fujitsu.com Graham Klyne Baltimore Technologies - Content Security Group, 1310 Waterside, Arlington Business Park Theale Reading, RG7 4SA United Kingdom. Telephone: +44 118 903 8000 Facsimile: +44 118 903 9000 E-mail: GK@ACM.ORG Sugano et al. [Page 20] INTERNET DRAFT CPIM Presence Format May 2002 Adrian Bateman VisionTech Limited Colton, Staffordshire, WS15 3LD United Kingdom E-mail: bateman@acm.org Wayne Carr Intel Corporation 2111 NE 25th Avenue Hillsboro, OR 97124 USA E-mail: wayne.carr@intel.com 10. Appendix A. Document Type Definitions The Document Type Definition for the "application/cpim-pidf+xml" format is described. The DTD here is presented only for informational for those who may not familiar with the XML Schema definition. Note: the DTD does not show where extension elements can be added. See the XML Schema for that information. Sugano et al. [Page 21] INTERNET DRAFT CPIM Presence Format May 2002 11. Full Copyright Statement Copyright (C) The Internet Society (2002). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Sugano et al. [Page 22]