Network Working Group M. Mealling Internet-Draft Network Solutions, Inc. Expires: May 18, 2001 November 17, 2000 URI Relationship Discovery via RESCAP draft-mealling-uri-rdf-00.txt 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 May 18, 2001. Copyright Notice Copyright (C) The Internet Society (2000). All Rights Reserved. Abstract Many emerging Internet applications use URIs to identify various protocol components. In many of these cases it is possible for a URI to be used as a value that was created outside the context of that application. This document describes an architecture using RESCAP and RDF to allow an application to discover basic relationships between the URI in question and its Resource. 1. Introduction Uniform Resource Identifiers[1] are the simplest layer of identification in the Application Layer of the Internet. A given URI has one and only one Resource. If two strings are syntactically the same according to the URI syntax rules then they are considered to be the same URI and, by definition, those two strings identify the same Resource. This simple system is very powerful and flexible since it makes no determination about types of Resources, URI Mealling Expires May 18, 2001 [Page 1] Internet-Draft URI Relationship Discovery November 2000 equivalence, relationshps between Resources, etc. Any system can specify its own rules. The downside of this is that if an application decides to allow any URI to be included in a particular field or if an application comes across a URI 'in the wild', it has no way of being able to make resonable assumptions about what that URI identifies. Does it identify an abstraction? Is it some instance of some abstraction? Is it part of a container? Can it be used as a name or is it just a short term locator? In many cases these questions boil down to two concepts: o does the URI have some well known characteristic such as persistence, naming semantics, addressing semantics, o what is the relationship between the URI and other URIs that identify other Resources that have a strong relationship with this Resource. I.e. if this Resource is in a container, what is the URI for the container, if this Resource is an instance, what is its abstract Resource?) The problem is finding a way to discovery these relationships given just the URI. This document proposes a solution based on URI Resolution using the Dynamic Delegation Discovery System to find a server to answer the questions and RESCAP to actually encode and ask the questions. The answers are encoded using the Resource Description Format. 2. Expressing relationships with RDF RDF is a subject/predicate/object data model that is used to express relationships between Resources identified by URIs. The primary serialization syntax for the data model is XML. At this point defining an RDF Schema for these and other relationships is a task that needs much wider discussion. For now we will only attempt to list and classify some of the potential relationships that need to be exposed: Identifier relationships: * Is this URI used as a name or locator? * Is this URI globally available or do I need local information to use it? * Is there a gateway available that can help me use this URI? * Is this URI persistent? Resource relationships: * Is the Resource identified by this URI an abstract thing or an instance of one? * If this Resource is an abstract Resource, can you give me an instance? * If this Resource is an abstract Resource, can you give me an instance? Mealling Expires May 18, 2001 [Page 2] Internet-Draft URI Relationship Discovery November 2000 * Is this Resource a collection or part of one? * If this Resource is a member of a collection, what is the URI for the collection? 3. Using RESCAP to retrieve the RDF While expressing these relationships is useful, there is still the issue of discovering how to ask those questions and to whom. This is where the DDDS URI Resolution application and RESCAP come into play. Using URI Resolution, an authoritative RESCAP server is located. Once located, this server is queried using RESCAP for the question, the result is the RDF relationships expressed above. References [1] Berners-Lee, T., Fielding, R.T. and L. Masinter, "Uniform Resource Identifiers (URI): Generic Syntax", RFC 2396, August 1998. Author's Address Michael Mealling Network Solutions, Inc. 505 Huntmar Park Drive Herndon, VA 22070 US Phone: +1 770-921-2251 EMail: michaelm@netsol.com URI: http://www.netsol.com Mealling Expires May 18, 2001 [Page 3] Internet-Draft URI Relationship Discovery November 2000 Full Copyright Statement Copyright (C) The Internet Society (2000). All Rights Reserved. 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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. Acknowledgement Funding for the RFC editor function is currently provided by the Internet Society. Mealling Expires May 18, 2001 [Page 4]