Network Working Group M. Mealling Internet-Draft L. Daigle Expires: January 11, 2002 VeriSign, Inc. July 13, 2001 Service Lookup System (SLS) draft-mealling-sls-00 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. This Internet-Draft will expire on January 11, 2002. Copyright Notice Copyright (C) The Internet Society (2001). All Rights Reserved. Abstract Developing technology to allow for truly internationalized Internet identifiers is proving a hard nut to crack within the framework of the existing DNS. At the same time, the DNS continues to do an excellent job at serving its original mandate for providing efficient mappings between machine-readable labels and network resources. What is not clear is whether the existing DNS can be transformed into a service that can handle the more human oriented identification services it is now being asked to provide. This document embraces, extends and complements a proposal by John Klensin to address the requirements for a directory layer above the existing DNS that can better solve these problems. The discussion concludes by proposing a Mealling & Daigle Expires January 11, 2002 [Page 1] Internet-Draft Service Lookup System July 2001 strawman called the Service Lookup System (SLS). 1. A Story From the Past Approximately 100,000 years ago a primitive human named Og was sitting in his cave examining his possessions. It had been a particularly good hunting season that year, and as a result, Og had a large number of furs, spears, and other cave man type stuff. Og began to be confused by the amount of stuff he had to manage so he began to give some of this stuff a name. The fur he was wearing became 'Og's Coat' and his spear became 'Og's Favorite Spear'. Things became manageable once again. One sunny prehistoric day, Og decided to take a walk. As he exited his cave he noticed a column of smoke a few miles away and decided to investigate, this being the unique trait of his species. As he approached the fire he noticed that it was burning in an arrangement similar to his own but this fire was burning next to a gracefully flowing river. There were items similar to his own next to the fire. As he approached closer he noticed a man sitting next to the fire working on an animal fur. It had been many years since Og had seen another person; thus, Og approached cautiously. The other cave man noticed Og and, as he approached, said "Hello. My name is Og. What is your name?" Og was quite startled by this development since he did not know what to make of someone claiming to be him. Perplexed by Og's silence, the other cave man held out the fur he was working and said, "This is Og's new fur coat. I call it 'Og's Coat'. What do you think of it?" This further perplexed Og since 'Og's Coat' was the coat that Og was currently wearing. Og finally broke his silence and explained this perplexing situation to the new cave man. This situation also concerned the new cave man since he also didn't know what to do with the idea of someone claiming to be him. After a few hours of halting discussion both men noticed a cave woman walking toward them from further down the river. As she approached she introduced herself as Og which completely fouled up each cave man's sense of identity. The cave woman was amused by their reaction and laughed out loud. The cave men stopped arguing and looked at her and asked how she could laugh at a time like this. She sat down next to Og's fire and began to explain to the cave men the new technological development of qualified names. To the original Og she said, "You are now known as Og From The Cave." To the new cave man she said, "And you are Og By The River." She held up Og By The River's coat and said, " The name of the coat is 'Og By The River's Coat'." Mealling & Daigle Expires January 11, 2002 [Page 2] Internet-Draft Service Lookup System July 2001 The two men looked at each other in amazement and expressed their gratitude to the cave woman for solving their problem. Finally they asked, "But what is your name?". She chuckled and said, "Og That Is Smarter Than Men". The moral of this story is this: if our ancestors discovered the ability of qualifying names with various facets such as location or category why do we insist on using a technology (DNS) that doesn't have this ability? This story has its origin with John Klensin and has been used in numerous conversations to illustrate the need for something above and beyond the DNS. 2. Introduction In "A Search-based access model for the DNS" [1], the author discusses approaching the problems of international domain-names and enhanced DNS with a layered approach that leaves the current DNS' form and function unmodified. The three layers are: Layer 1 -- The DNS, with the existing lookup mechanisms Layer 2 -- A restricted lookup system where the identifiers are qualified by additional attributes called facets. Facets include concepts such as locale and category. Layer 3 -- Commercial, localized, and topic-specific search environments. This memo discusses the technical and policy problems and solutions for a Layer 2 service. 3. The Problem Statement Roughly stated, the goal of Layer 1 is to provide unique, machine friendly identifiers for network level resources that can be used as protocol elements. Layer 3 is for search services such as search engines (Google) and localized/topic specific directory services (LDAP); e.g. very human and/or task specific services. Layer 2 attempts to be a bridge between Layer 1 and Layer 3. The problem is: what is the functional and deployable middle ground? This includes even the fundamental question of exactly what is the problem Layer 2 will attempt to solve? Much of the discussion to date surrounding this topic has been directly associated with internationalization of Internet identifiers (specifically domain-names). For Western cultures the need for anything beyond simple matches on characters is not immediately apparent. Since the Internet, and DNS specifically, were designed Mealling & Daigle Expires January 11, 2002 [Page 3] Internet-Draft Service Lookup System July 2001 using Western characters, it is much easier for Western speakers to learn to live with the limitations and thus those limitations aren't as glaringly apparent. But when confronted with other character sets from Asian languages, the simple "match on characters" semantic quickly becomes unworkable and in many cases fundamentally cannot address the identification requirements of the user. Requirements such as 'match based on the locale of the querier' and 'order of the name components to match user expectation' have been common enough to illustrate that, at least for some not insignificant portion of the participants, the problems that are attempting to be solved are beyond DNS' capabilities. It is exactly the work being done in the IDN Working Group that is bringing these problems to light. It is also interesting to look at what might be the root cause of all of these problems. In the authors' opinion, many of these problems stem from the disconnect between what the DNS was meant to identify and what it is actually being used for. In many cases the DNS is being used to identify complex services that have no concrete network level representation. When a user types 'cnn.com' into a web browser they are not explicitly asking for the index.html file at the root level context of the HTTP server running on the default port of the host 'cnn.com'. The user's view of the process is that he/she is requesting the current news from CNN via the Internet. The problem is that IDN and similar efforts are attempting to force the user's service-oriented view of the world into a network protocol view. The various problems and feature desires discussed in the IDN process involve some of the following: o Character sets -- Full Unicode support at a minimum. There is some desire to enable other character sets but most comments have said that mapping into Unicode is acceptable as long as there can be some method for communicating what locale was used for doing that mapping. o Localization -- In some cases there are semantic differences in what an appropriate match should be that are based on location, jurisdiction, or region specific dialect. o Geographic scoping -- In some cases, it is appropriate to distinguish between identifiers based on the region or geographical scope of applicability. For example, trademarks have traditionally been scoped by geographical boundaries. o Category based scoping -- To fully handle most trademark law and the human habit of using the same word to mean two different things, names also need to be scoped by the category they fit into. The problem here is to figure out which categories to use Mealling & Daigle Expires January 11, 2002 [Page 4] Internet-Draft Service Lookup System July 2001 since there is no single taxonomy in which all things can be categorized. o Syntactic sugar -- If at all possible, the system should not place synthetic syntactic restrictions or requirements on identifiers. One main reason is that there are no common syntactic elements among all languages. This includes both computational, structured syntax (e.g. dot separators) and no requirements or constraints on the interpretation of the identifier (e.g. any Unicode character is valid). 3.1 Interesting DNS Characteristics While the goal of Layer 2 is to be human-friendly, it is still a lookup service that must be sufficiently deterministic so that higher level services can be built which will give the user a consistent experience. Some of the DNS' current characteristics are worth emulating because it is sufficiently deterministic to support building services. The important characteristics are: o limited match semantics (lookup only) o Deterministic relationship between the name and the answer set o all public names are globally available o in the case of an A record, the result is service independent. The client can use the result for multiple purposes by connecting to any service specific port on the host instead of requiring with a per service query. o query routing is based on the hierarchical structure of the name that is being looked up. One of the fundamental differences between the DNS and a Layer 2 service is that, with DNS, the user is required to know exactly which answer set they need in the form of the name being looked up. This leads to practices such as putting a 'www' as a third level domain- name in order to denote the kind of service the user is requesting. This is primarily caused by the lack of additional parameters that can be sent by a DNS query, resulting in any 'parameters' being part of the name being looked up. The additional fact that a name can only match one discrete answer set means that a client cannot ask an intentionally ambiguous question about a name and get two complete answers back or have the same name be differentiated by a parameter. Mealling & Daigle Expires January 11, 2002 [Page 5] Internet-Draft Service Lookup System July 2001 One of the goals of a good Layer 2 service would be to separate the uniqueness of the results record set from the name used to lookup that record set. This does result in the case where a client may be required to disambiguate between two or more record sets when the client does not provide sufficient information in the query for the service to do the disambiguation. This case may arrise when the query does not include all of the facets or when one of the facets is intentionally not fully specified (i.e. a location that is specified to be an entire continent instead of some specific city). Another question is whether or not any query routing algorithms are based on structure requirements of the names themselves. Unlike the DNS, the Layer 2 service has facets that can be used to route queries. In this case there is no need for that structure to be in the name, and since such structure would be injurious to the goal of being as human-friendly as possible, hierarchy requirements are moved to the facet that requires it instead of into the name itself. I.e., the facet system is multi-hierarchical, while the names themselves are flat. 3.2 Requirements Decisions The above analysis simply illustrates many questions and possible answers. The more obvious requirements from the above are: o Names are, at the very least, encoded using the complete Unicode codeset without restriction and without normalization. o At the very least, locale is a supported facet, both as an optional query component and as part of the result set. o Uniqueness is an important characteristic of DNS that should be emulated by some aspects of the system, though which aspects and how are uncertain. It is at least a requirement that a given name/facet set/service tuple be unique. o There are no requirements that the names are structured o There are requirements that facets be structured, highly standardized, limited in number and with values that come from controlled vocabularies. o It should be possible for a result to identify a service independent network node so that the client may contact that node for multiple services without having to re-query the Layer 2 service again and again for each different service. o While locale in its various standardized forms does communicate Mealling & Daigle Expires January 11, 2002 [Page 6] Internet-Draft Service Lookup System July 2001 some aspects of 'location', additional information is needed in order to support various human assumptions such as trademark law and locality of reference (geographic and category scoping). o Entries must be globally unique, but 2 entries may be distinguishable by as little information as the service through which they are made available. In other words, names and their facets, as a whole, are unique within a service and are scoped to that service. o A result must return its entire context. This includes not only the name and the identification component but ALL of the facets that made up the match. o There are no requirements or restrictions on the entities that can be identified. A name can apply to a human, a corporation, etc. Some services may not make sense for a given entity but that it simply reflected in that name simply not begin registered with a provider for that service type. o It is expected that Layer 2 services will be provided on a competitive basis. This means multiple service providers that may cover the same areas and who compete directly with each other. The concept of Layer 2 'service providers' has been mentioned several times so far and needs to be discussed itself. In order to avoid requiring a single, structured global delegation of registration and lookup servers, we start from the assumption that there will be multiple independent collections of name/facets. Name/facet tuples must be globally unique across all publicly accessible collections. This is accomplished by including the service provider as one of the facets; essentially making name/facet tuples unique to their provider. Beyond this there is no other defined relationship between service providers. Whether providers coordinate or compete with each other is beyond the scope of this document. The only material effect is that we need to determine whether "discovery" is a required component of the Layer 2 query protocol. There may be a requirement that a tuple have a service provider independent and globally unique identifier to allow for a tuple to 'migrate' from provider to provider but this is more of a policy requirement than a technical one. Questions still to be answered are: o Is Unicode sufficient? If not by itself then is a mapping from the local character set onto Unicode provided the mapping used is communicated to the service via the locale facet sufficient? If not, then is the requirement that _all_ character sets be Mealling & Daigle Expires January 11, 2002 [Page 7] Internet-Draft Service Lookup System July 2001 supported? o In many cases 'locale' is a combination of pieces of information. The value associated with any Posix locale setting is a combination of the ISO 3166-1 two letter country code and a two letter language code. Is this concept of locale sufficient for the boundary cases found in some languages? Does the definition need to be augmented by ISO 3166-2 subregion codes? Are the standard two letter language codes also sufficient? o Is uniqueness based on the name/facet-set/service tuple sufficient? o If it is, is there a requirement that the results of a query be exhaustive? This requirement would create a situation where all service providers would have to be discoverable. o Is there a real requirement for supporting the trademark law concepts of name scoping by geographic and category boundaries? If so then requirements for the location and category facets need to be investigated further. 4. A Strawman Proposal: The Service Lookup System (SLS) 4.1 Network Service Record (NSR) Many of the stresses and strains being put on the DNS stem from the fact that it was designed as a simple name to number mapping system for network machines, but is now being called upon to be the tool to map from real world entities (companies, individuals, services) into network services. Since networks are designed and evolve to meet technical and network administration needs, their evolution is often at odds with that of the services that real world entities (individuals, organizations) wish to communicate about. This stress is particularly noticeable in the identifier strings themselves (domain and host names) -- companies, individuals and services must be named using labeling conventions that were devised for network machines. This simply doesn't fit. Network Service Records (NSRs) act as the "glue" between real world entities and network services. They do not replace the DNS in form or function. These are administrative records, containing information that will allow users to identify (recognize) real world entities. They can be used on an occasional basis to obtain specific network (machine interpretable) identifiers. NSRs are different than URIs, which are machine interpretable names Mealling & Daigle Expires January 11, 2002 [Page 8] Internet-Draft Service Lookup System July 2001 and addresses providing specific identification. In fact, the network identifiers provided in the NSR are URIs. The results of an NSR lookup may be stored in user software (e.g., bookmark lists, caches, mail address books, buddy lists). Done right, the NSR label will be interpretable by human users (perhaps even attaining the elusive goal of "human friendliness") while DNS and other network identifiers continue to evolve to meet technical needs (necessarily not being "human-friendly" to the bulk of the world's population). The format of an NSR is undefined here since it is more likely to be dependent on the requirements of the service used to look them up. In the strawman SLS proposal below the format is inherited from the ResourceDescriptor element from CNRP. 4.2 Content of the NSR The NSR contains, minimally, an identifier label and several other elements of descriptive information concerning the network service. These are called "facets" of the network service. Additionally, the NSR contains identifiers for specific network services registered in the NSR. NSRs are globally unique across the label AND descriptive facet data. That is, many NSRs may have the same label, if they differ in the values of other facet data. 4.3 NSR Population NSRs are registered on an opt-in basis. An organization or individual wishing to identify their network service(s) through a particular label may register the label and associated facet information with any NSR registry service, pursuant to the uniqueness criteria mentioned above. It is not expected that domain name holders, organizations, or individuals will register an NSR for each host name within their domain. Rather, the NSR is independent of network devices. One service (e.g., what we today know of as an HTTP server operating for a particular domain) may have several NSRs to reflect different labels for the service entity. And, that may be the only "machine" within an organizations network that has an NSR registered to identify its services. All network services are accessible through the traditional, existing network identifiers (host+port+protocol, URIs, etc). Mealling & Daigle Expires January 11, 2002 [Page 9] Internet-Draft Service Lookup System July 2001 4.4 Service Lookup System (SLS): Looking up NSRs The basic lookup operations that are considered valid for effecting NSR to network service identifier mappings are: o NSR label (required, whole string) o NSR descriptive facets (optional, substring allowed) o Target Service (required, from designated list of possible) o Additional descriptive data about the user's linguistic and geographic preferences (optional) The NSR label is required, in full, since this is a lookup service not a data mine. That being said, individual NSR directory services may apply local matching heuristics to retrieve NSRs that are "like" what the user is looking for, at their discretion, and in order to accommodate potential difficulties in matching transcriptions. Additionally, NSR directory services may use the additional user descriptive information (language, locale, etc) to determine a match against the set of NSRs it has. The response to an NSR lookup request will be 0 or more NSRs. 4.5 Services The target services are: 'dns' -- Any DNS record type designated by the 'dns:' URI scheme [2]. The service facet in the query for the NSR(s) is specified in the form of 'dns::'. For example, to request an MX record the service would be 'dns:1:15'. 'web' -- The request is for the URI of a web page used for browsing by a user. The result SHOULD either be a URI with the 'http' scheme or a 'dns:' URI pointing to the A record(s) for the web server. 'email' -- In general, the NSR is targeted at identifying network services as a whole. This is useful in solving today's problem of trying to support catchy phrases for identifying a corporation's main website, but is not useful for replacing e-mail addresses on business cards. Insofar as e-mail addresses comprise identification of particulars (string on the lefthand side of the "@") at a particular service (SMTP), it is not a far stretch to think of developing a companion Mealling & Daigle Expires January 11, 2002 [Page 10] Internet-Draft Service Lookup System July 2001 standard to identify particulars within a given service. That is, the NSR could be used to find the network location of the particular service, and then the particular identifier would be mapped into the local part of the network address. Although the conventions for expressing NSR label and the particular identifier (e.g., on a business card) are well beyond the scope of this document, consider for example: I might express my e-mail service as: Leslie Daigle at Le Chat Pensant The SLS service will provide a DNS URI that identifies either an MX or A record for the relevant SMTP service (thinkingcat.com) as well as a referral to another SLS service that can map "Leslie Daigle" to some value that is valid for that SMTP service (in this case 'leslie'), yielding 'leslie@thinkingcat.com' to be stored in an e-mail address book. 4.6 Mapping the SLS onto CNRP As part of the proposal the SLS is mapped onto the Common Name Resolution Protocol (CNRP) [3]. CNRP was designed to handle services with many of the same requirements and thus makes an easy match for discussing particular aspects of the proposal. One important issue is that operational requirements may require that the XML encoding and HTTP transports be dropped in favor of something with a smaller network 'footprint'. 4.6.1 An Introduction to the Common Name Resolution Protocol (CNRP) CNRP is a protocol that is encoded in XML and transported via HTTP (as mandatory to implement, other transports are valid). The basic component of CNRP is the 'Common Name'. This is the item that is being looked up. In addition to the Common Name, a query can contain Properties. Properties have names and types. A Property type is an identifier for which controlled vocabulary the value is drawn from. CNRP general feature list includes: o Unicode -- While standard XML conventions allow for specifying additional language and character set values, CNRP is required to be expressed in Unicode using the encoding specified in the XML Mealling & Daigle Expires January 11, 2002 [Page 11] Internet-Draft Service Lookup System July 2001 document header. o Referral support -- A CNRP server can send a message to the client which tells the client what server and possible dataset an answer might be found in. o No requirements on the CN -- CNRP makes no other requirements on the CN other than being expressed in Unicode. o No requirements on match semantics -- CNRP puts no requirements on a service provider as to what match semantics they may or may not use. The query is series of hints only. It is up to other standards to define services using CNRP that adhere to specific rules. o Only three Properties defined -- CNRP defines the Location, Language and Category properties in addition to a process for defining new Properties. Results within CNRP are encoded as ordered sets of either referrals, status codes or ResourceDescriptors. It is the ResourceDescriptor which is used as the encoding of the NSR. The following is an example of a ResourceDescriptor acting as an NSR returned in response to a query for the name 'Joe's Example Mart': http://sls.bar.com/ Joe's Example Mart foo.com:234364 http://acme.example.com/~joe/examples/ A purveyor of fine examples en-uk gb-ham web 380023 Mealling & Daigle Expires January 11, 2002 [Page 12] Internet-Draft Service Lookup System July 2001 4.6.2 CNRP Service Definition 4.6.2.1 CNRP Properties as Facets The concept of facets is handled with CNRP properties. Properties have both a name and a type. Properties can be valid for either queries or results or both. The location property has a new type defined that is hierarchical in nature with each level separated by a "-". The first level is taken from ISO-3166-1 two letter country codes. The second level is taken from ISO-3166-2. Third and subsequent levels are defined by the previous level. For example, the city of Lubbock, Texas would use: us-tx-lubbock. The language property is restricted to the values found in RFC 3066 [5] The type of the category property is 'nice' which designates the classification of goods and services found in the Nice Agreement on International Classification of Products and Services [4]. The service property is the type of service being requested. The list of services is made up of the complete list of DNS QTYPEs and QCLASS-es plus specific services defined in Section 4.5. The format of the service designator is defined by each service. The source service ID is a required CNRP property but it is listed here to be sure to note that uniqueness discussed earlier includes the source of the results as one of the facets that determine uniqueness. 4.6.2.2 Service Object XML SLS defines a new CNRP property called 'cnrp-service-type' which is used to notify the client that this service adheres to the SLS standard. This is why the service object doesn't actually need to define all of the SLS facets as CNRP properties. Mealling & Daigle Expires January 11, 2002 [Page 13] Internet-Draft Service Lookup System July 2001 urn:foo:bar http://host1.example.com:4321 mailto:user@example.com This is the ExampleCorp SLS Service sls cnrp-service-type iana 4.6.3 Contextual Uniqueness A CNRP service MUST have one and only one answer for any COMPLETE set of facets. This includes the facet that is the service name itself. This means that essentially uniqueness of a given name is at the service level. Thus, if a query is sent to more than one service, each one may send back valid answers. These are considered different NSRs (because they differ in the service facet). Also, if a particular facet is set to a higher level of some hierarchical value or set to a wildcard type match semantic, it is also possible to get multiple answers for the query. What this means and how applications should deal with it is up for discussion since this behavior is the one aspect of Layer 2 that directly affects Mealling & Daigle Expires January 11, 2002 [Page 14] Internet-Draft Service Lookup System July 2001 usability. 4.6.4 Results Restrictions Results are in the form of URIs. Unlike a generic CNRP service the schemes that can be returned are explicitly defined to match the Service facet in the request. See Section 4.5 for the list of Service to Results URI matchings and the semantics of those matches. 4.7 Example Scenarios The following scenarios show how a few services might be used in 'real world' situations. 4.7.1 The DNS Service The DNS SLS service is meant more as a method for moving from the currently deployed infrastructure to new, SLS based systems. Imagine an English speaking user living in Lubbock, Texas who is attempting to browse the CNN web site. The user has pre-configured two SLS providers but her implementation does not understand any services beyond the 'dns' service. The first provider is scoped to her metropolitan area and the second handles names with a more global scope. The user attempts to ask for the 'dns:1:1' service for the name 'CNN' with their location set to 'us-tx-lubbock', their language (locale) set to 'en-us'. They leave the category blank. The query is sent to both the locally and globally scoped services. The locally scoped service returns no results and the global one returns the URI 'dns:www.cnn.com;type=a'. The same scenario could work for leveraging legacy services such as ftp, instant messaging and even email (if applied carefully). The exact transaction between the client and server looks like this. The client connects to the server (over some transport) and issues this request: Mealling & Daigle Expires January 11, 2002 [Page 15] Internet-Draft Service Lookup System July 2001 C: C: C: C: C: cnn C: us-tx-lubbock C: en-us C: C: dns:1:1 C: C: S: S: S: S: S: S: http://example.com S: S: S: CNN S: 1333459455 S: dns:www.cnn.com;type=A S: S: The Cable News Network (tm) S: global S: en-us S: 380012 S: web S: S: S: 4.7.2 The Web Service The end goal is a more task specific service query. Take the previous scenario as a starting point but instead the user's client can understand the 'web' service. In this case the user is interested in the 'CNN Travel' name. They send the same query to both services and again the locally scoped one returns nothing but the globally scoped one returns the URI 'http://www.cnn.com/TRAVEL/'. Note how the name given by the user is all lower case but it matches the upper case. This can safely be done because the locale specifies sorting and matching algorithms specifically. The entity that Mealling & Daigle Expires January 11, 2002 [Page 16] Internet-Draft Service Lookup System July 2001 registered the name can specify whether or not the name is case sensitive or not. Again, the actual XML sent looks like this: C: C: C: C: C: cnn travel C: us-tx-lubbock C: en-us C: C: web C: C: S: S: S: S: S: S: http://example.com S: S: S: CNN Travel S: 1333459455 S: http://www.cnn.com/TRAVEL/ S: S: The Cable News Network: Travel S: Section(tm) S: global S: en-us S: 380012 S: web S: S: S: 4.7.3 The Web Service With Ambiguous Results Now, imagine the last scenario but with the name as "John's Computer Repair". In this case the user still asks for the 'web' service but the locally scoped provider returns one result and the globally Mealling & Daigle Expires January 11, 2002 [Page 17] Internet-Draft Service Lookup System July 2001 scoped one also returns a result. The one returned by the locally scoped provider is for a computer repair company just down the street from the user. The one from the globally scoped provider is for a computer repair company that advertises around the world. The user's client presents the user with a choice between the two and the user chooses. In this case the exact same query is sent to both servers: C: C: C: C: C: john's computer repair C: us-tx-lubbock C: en-us C: C: web C: C: The locally scopped server returns this: S: S: S: S: S: S: http://lubbock-tx-example.com S: S: S: John's Computer Repair S: 1333459455 S: http://www.lubbocknet/~john/ S: S: Serving the Lubbock, TX computer user since 1948 S: S: us-tx-lubbock S: en-us S: 370166 S: web S: S: S: Mealling & Daigle Expires January 11, 2002 [Page 18] Internet-Draft Service Lookup System July 2001 while the globally scoped one returns this: S: S: S: S: S: S: http://example.com S: S: S: John's Computer Repair S: 1333459455 S: http://www.computer-repair.biz/ S: S: Worldwide hardware repair and software consulting S: via mail order S: global S: en-us S: 370166 S: web S: S: S: 4.7.4 The Web Service With Ambiguous Query and Results The previous example can also happen when the user specifies an ambiguous, blank or multivalued facet. For example, since the user never specified a category, "John's Computer Repair" could have matched several different NSRs that had the same name but different facet values. A more likely example would be 'Genesis' (the band and the hydraulics company). If the user were to specify a query for Genesis and left the category blank then the user could consievably get a large number of answers back: Mealling & Daigle Expires January 11, 2002 [Page 19] Internet-Draft Service Lookup System July 2001 C: C: C: C: C: Gensis C: us-tx-lubbock C: en-us C: C: web C: C: which would return in a series of results: S: S: S: S: S: S: http://example.com S: S: S: Genesis S: 1333459455 S: http://www.sony.com/genesis S: S: The band S: global S: en-us S: 410023 S: web S: S: S: Genesis S: 2345432 S: http://www.genesis-hydraulics.com/genesis S: S: S: Providing world wide hydraulics engineering S: services sinde 1973 S: global S: en-us S: 370166 S: web Mealling & Daigle Expires January 11, 2002 [Page 20] Internet-Draft Service Lookup System July 2001 S: S: S: .... other results from other categories S: S: S: References [1] Klensin, J., "A Search-based access model for the DNS", Internet Draft draft-klensin-dns-search-00.txt, May 2001, . [2] Josefsson, S., "DNS URL scheme", Internet Draft draft-josefsson- dns-url-01.txt, June 2001, . [3] Popp, N., Mealling, M. and M. Moseley, "Common Name Resolution Protocol (CNRP)", Internet Draft draft-josefsson-dns-url-01.txt, June 2001, . [4] World Intellectual Property Organization, "Nice Agreement concerning the International Classification of Goods and Services for the Purposes of the Registration of Marks", June 1957. [5] Alvestrand, H., "Tags for the Identification of Languages", BCP 47, RFC 3066, January 2001. Authors' Addresses Michael Mealling VeriSign, Inc. 21345 Ridgetop Circle Sterling, VA 20166 US EMail: michael@research.netsol.com URI: http://www.verisign.com Mealling & Daigle Expires January 11, 2002 [Page 21] Internet-Draft Service Lookup System July 2001 Leslie Daigle VeriSign, Inc. 21345 Ridgetop Circle Sterling, VA 20166 US EMail: leslie@research.netsol.com URI: http://www.verisign.com Mealling & Daigle Expires January 11, 2002 [Page 22] Internet-Draft Service Lookup System July 2001 Full Copyright Statement Copyright (C) The Internet Society (2001). 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. 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Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society. Mealling & Daigle Expires January 11, 2002 [Page 23]