Contents

• Overview of RDF
• RDF Resources at W3C
• RDF Specifications
  • RDF Model and Syntax Specification
  • RDF Schema Specification
  • Related W3C Documents
• General: News, Articles, Papers on RDF
• Software Tools for RDF
• Other RDF Resources

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Overview of RDF

This RDF document currently provides information and references for both the Resource Description Framework (RDF) Model and Syntax Specification and the Resource Description Framework (RDF) Schema Specification. References are given for articles/papers, in addition to RDF software. A more complete RDF reference collection, in many respects, is "Dave Beckett's Resource Description Framework (RDF) Resource Guide."

"RDF (Resource Description Framework) is a framework for metadata; it provides interoperability between applications that exchange machine-understandable information on the Web. RDF emphasizes facilities to enable automated processing of Web resources. RDF metadata can be used in a variety of application areas; for example: in resource discovery to provide better search engine capabilities; in cataloging for describing the content and content relationships available at a particular Web site, page, or digital library; by intelligent software agents to facilitate knowledge sharing and exchange; in content rating; in describing collections of pages that represent a single logical 'document'; for describing intellectual property rights of Web pages, and in many others. RDF with digital signatures will be key to building the 'Web of Trust' for electronic commerce, collaboration, and other applications." [from the W3C FAQ document]

Resource Description Framework (RDF) "provides a more general treatment of metadata. RDF is a declarative language and provides a standard way for using XML to represent metadata in the form of statements about properties and relationships of items on the Web. Such items, known as resources, can be almost anything, provided it has a Web address. This means that you can associate metadata with a Web page, a graphic, an audio file, a movie clip, and so on. RDF provides a framework in which independent communities can develop vocabularies that suit their specific needs and share vocabularies with other communities. In order to share vocabularies, the meaning of the terms must be spelled out in detail. The descriptions of these vocabulary sets are called RDF Schemas. A schema defines the meaning, characteristics, and relationships of a set of properties, and this may include constraints on potential values and the inheritance of properties from other schemas. The RDF language allows each document containing metadata to clarify which vocabulary is being used by assigning each vocabulary a Web address. The schema specification language is a declarative representation language influenced by ideas from knowledge representation (e.g., semantic nets, frames, predicate logic) as well as database schema specification languages and graph data models. RDF uses the idea of the XML namespace to effectively allow RDF statements to reference a particular RDF vocabulary or 'schema'. [From the W3C Metadata Activity page]

The Resource Description Framework (RDF) is a specification governing the interoperability of applications in terms of metadata property sets. It is being developed under the authority of the W3C in the context of the W3C Metadata activity. The draft specifications from W3C confirm that "RDF will use XML as the transfer syntax in order to leverage other tools and code bases being built around XML..." The collaborative RDF effort is based upon several other metadata initiatives; the working group responsible for the draft is composed of "key industry players including DVL, Grif, IBM, KnowledgeCite, LANL, Microsoft, Netscape, Nokia, OCLC, Reuters, SoftQuad and University of Michigan." "RDF metadata can be used in a variety of application areas such as: (1) in resource discovery to provide better search engine capabilities; (2) in cataloging for describing the content and content relationships available at a particular Web site, page, or digital library; (3) by intelligent software agents to facilitate knowledge sharing and exchange; (4) in content rating for child protection and privacy protection; (5) in describing collections of pages that represent a single logical "document"; (6) for describing intellectual property rights of Web pages." [press release October 3, 1997]

"RDF is the result of a number of metadata communities (including Dublin Core, PICS, Digital Signatures) bringing together their needs to provide a robust and flexible architecture for supporting metadata on the Internet and WWW. RDF will use the new XML as its main carrier syntax." [from the DSTC page, where the Resource Description Framework is listed as a Resource Discovery Unit 'Special Project']

RDF Resources at W3C

• Resource Description Framework (RDF). W3C Main Page

• RDF FAQ Document, from W3C

• W3C Metadata Activity Statement. Explains W3C's plans for RDF and metadata in detail. Work on Metadata is part of W3C's Technology and Society Domain.

• RDF Interest Group. "The RDF Interest Group was established in August 1999 as an open forum for W3C Members and non-Members to discuss issues relating to W3C's Resource Description Framework." See the RDF IG Charter and the archives of the RDF-Interest mailing list ['www-rdf-interest@w3.org'].

• [August 30, 2002] "Resource Description Framework (RDF): Concepts and Abstract Data Model." Edited by Graham Klyne (Clearswift and Nine by Nine) and Jeremy Carroll (Hewlett Packard Labs). Series editor: Brian McBride (Hewlett Packard Labs). W3C Working Draft 29-August-2002. Version URL: http://www.w3.org/TR/2002/WD-rdf-concepts-20020829/. Latest version URL: http://www.w3.org/TR/rdf-concepts/. Produced by the W3C RDF Core Working Group as part of the W3C Semantic Web Activity. The Resource Description Framework (RDF) is a data format for representing metadata about Web resources, and other information. This document defines the abstract graph syntax on which RDF is based, and which serves to link its XML serialization to its formal semantics. It also describes some other technical aspects of RDF that do not fall under the topics of formal semantics, XML serialization syntax or RDF schema and vocabulary definitions (which are each covered by a separate document in this series). These include: discussion of design goals, meaning of RDF documents, key concepts, character normalization and handling of URI references... The normative documentation of RDF falls broadly into the following areas: (1) XML serialization syntax [RDF/XML Syntax Specification (Revised)]; (2) formal semantics [RDF Model Theory]; (3) RDF vocabulary definition language (RDF schema) [RDF Vocabulary Description Language 1.0: RDF Schema], and (4) this document, which covers the following: discussion of design goals, meaning of RDF documents, key concepts, abstract graph syntax, character normalization, and handling of URI references..."

• [September 12, 2001] RDF Test Cases. W3C Working Draft 12-September-2001. Version URL: . Latest Public Version URL: http://www.w3.org/TR/rdf-testcases/. Edited by Art Barstow (W3C) and Dave Beckett (ILRT, University of Bristol). The document describes the RDF Test Cases deliverable for the RDF Core Working Group as defined in the WG's Charter. It describes the test cases that will fullfill (when the test cases are completed) that deliverable but it does not contain the test cases themselves; the test cases are available at http://www.w3.org/2000/10/rdf-tests/rdfcore/. Background: "The W3C RDF Interest Group and other members of the RDF community have identified issues/ambiguities in the RDFMS Specification and the RDFSchema Candidate Recommendation. These issues have been collected and categorized in the RDF Issue Tracking document. The RDF Core Working Group uses this issue list to guide its work..."

• W3C 'www-rdf-logic@w3.org' mailing list, and archives. The list provides "a forum for technical discussion concerning the design of logic-based languages for use on the Web. W3C provides the www-rdf-logic forum as a home for detailed technical discussion of all approaches to the use of classical logic on the Web for the representation of data such as inference rules, ontologies, and complex schemata. The logic list, through association with the RDF Interest Group, also serves as a mechanism to provide input into W3C's Semantic Web activities, in particular relating to future directions for the Resource Description Framework."

• W3C 'www-rdf-specs@w3.org' mailing list, and archives

• "Introduction to RDF Metadata." By Ora Lassila. W3C NOTE 1997-11-13. NOTE-rdf-simple-intro-971113.html. [cache]

• W3C Contacts for RDF/Metadata Activity [2000-10-02]:

  • Ralph Swick, W3C Metadata Activity Leader
  • Eric Miller and Bob Schloss, RDF Model and Syntax Chairs emeritus
  • Eric Miller, RDF Schema Chair
  • David Singer, RDF Schema Chair emeritus
  • Dan Brickley, RDF Interest Group Chair

W3C RDF Specifications

[February 10, 2004]   W3C Recommendations: Resource Description Framework (RDF) and Web Ontology Language (OWL).    The World Wide Web Consortium has announced "final approval of two key Semantic Web technologies, the revised Resource Description Framework (RDF) and the Web Ontology Language (OWL). RDF and OWL are Semantic Web standards that provide a framework for asset management, enterprise integration and the sharing and reuse of data on the Web. These standard formats for data sharing span application, enterprise, and community boundaries, since different types of users can share the same information even if they don't share the same software." The Resource Description Framework (RDF) is a "language for representing information about resources in the World Wide Web. It is particularly intended for representing metadata about Web resources, such as the title, author, and modification date of a Web page, copyright and licensing information about a Web document, or the availability schedule for some shared resource. However, by generalizing the concept of a 'Web resource', RDF can also be used to represent information about things that can be identified on the Web, even when they cannot be directly retrieved on the Web. Examples include information about items available from on-line shopping facilities (e.g., information about specifications, prices, and availability), or the description of a Web user's preferences for information delivery." The W3C RDF Recommendation is presented six parts: Primer, Concepts, Syntax, Semantics, Vocabulary, and Test Cases. The OWL Web Ontology Language is "intended to be used when the information contained in documents needs to be processed by applications, as opposed to situations where the content only needs to be presented to humans. OWL can be used to explicitly represent the meaning of terms in vocabularies and the relationships between those terms. This representation of terms and their interrelationships is called an ontology. OWL has more facilities for expressing meaning and semantics than XML, RDF, and RDF-S, and thus OWL goes beyond these languages in its ability to represent machine interpretable content on the Web. OWL is a revision of the DAML+OIL web ontology language incorporating lessons learned from the design and application of DAML+OIL." W3C has published the OWL Recommendation in six documents: Use Cases, Overview, Guide, Language Reference, Test Cases, and Language Semantics and Abstract Syntax.

RDF Recommendations 2004-02:

• RDF Primer
• RDF Concepts and Abstract Syntax
• RDF/XML Syntax Specification (Revised)
• RDF Schema
• RDF Semantics
• RDF Test Cases
• See also: Resource Description Framework (RDF) Model and Syntax Specification. W3C Recommendation 22-February-1999.
• See also: Resource Description Framework (RDF) Schema Specification. W3C Proposed Recommendation 03-March-1999,

Short list [2002-11], substituting for subsequent material that needs editing:

• RDF Primer (W3C Working Draft 11 November 2002)
• RDF Semantics (W3C Working Draft 12 November 2002)
• RDF Vocabulary Description Language 1.0: RDF Schema (W3C Working Draft 12 November 2002)
• RDF/XML Syntax Specification - Revised (W3C Working Draft 8 November 2002)
• Resource Description Framework (RDF): Concepts and Abstract Syntax (W3C Working Draft 08 November 2002)
• RDF Test Cases (W3C Working Draft 12 November 2002).

General: News, Articles, Papers on RDF

• [March 29, 2005]   W3C Releases Survey of RDF/Topic Maps Interoperability Proposals Working Draft.    An initial public working draft from the W3C RDF/Topic Maps Interoperability Task Force (RDFTM) presents A Survey of RDF/Topic Maps Interoperability Proposals. This specification, initiated by the W3C Semantic Web Best Practices and Deployment Working Group (SWBPD) with the support of the ISO Topic Maps Committee (ISO/IEC JTC1/SC34), is part of the W3C Semantic Web Activity. The document "contains a survey of existing proposals for integrating RDF and Topic Maps data and is intended to be a starting point for establishing standard guidelines for RDF/Topic Maps interoperability." The W3C Resource Description Framework (RDF) is a model developed by the W3C for representing information about resources in the World Wide Web. Topic Maps, a project of ISO/IEC JTC1/SC34, is a standard for knowledge [representation and] integration, developed by ISO. The primary goal of this W3C endeavor is to "achieve interoperability between RDF and Topic Maps at the data level. This means that it should be possible to translate data from one form to the other without unacceptable loss of information or corruption of the semantics. It should also be possible to query the results of a translation in terms of the target model and it should be possible to share vocabularies across the two paradigms." According to the Background statement for the Working Draft, the RDF and Topic Maps specifications "were developed in parallel during the late 1990's within their separate organizations for what at first appeared to be very different purposes. The results, however, turned out to have a lot in common and this has led to calls for their unification." While unification of RDF and Topic Maps has to date "not been possible, for a variety of technical and political reasons, a number of attempts have been made to uncover the synergies between RDF and Topic Maps and to find ways of achieving interoperability at the data level. There is now widespread recognition within the respective user communities that achieving such interoperability is a matter of some urgency. Work has therefore been initiated by the Semantic Web Best Practices and Deployment Working Group of the W3C with the support of the ISO Topic Maps committee to address this issue." This Working Draft "consists of a summary and analysis of the major existing proposals for achieving data interoperability between RDF and Topic Maps. RDF-Schema and OWL are considered relevant to this work to the extent that the classes and properties they define are supportive of its goals. However, it is explicity not a goal of the current work to enable the general use of RDF Schema and OWL with Topic Maps, although this issue may be addressed later.

• [December 03, 2003] "Styling RDF Graphs with GSS." By Emmanuel Pietriga. From XML.com (December 03, 2003). ['Visualising RDF graphs is a hard problem, as they can quickly become unwieldy. This article introduces a solution in the form off GSS (Graph Style Sheets), an RDF vocabulary for describing rule-based style sheets used to modify the visual representation of RDF models represented as node-link diagrams.'] "RDF models describe web resources using subject-predicate-object triples. Combined together, these triples form a graph structure, which cannot be easily conveyed by textual syntaxes such as RDF/XML, Notation 3 or N-Triple because of their one-dimensional nature. Visual editors such as IsaViz and RDF Author represent models as editable node-link diagrams, making the graph structure easier to understand compared to textual serializations. However, visual representations are not fully satisfying and have their own problems: diagrams can quickly become big and over-cluttered, and some editing tasks can be more difficult to achieve when dealing with a visual representation of the model. The first version of IsaViz offered partial solutions to these problems, such as a zoomable user interface combined with enhanced navigation capabilities... GSS (Graph Style Sheets) is an RDF vocabulary for describing rule-based style sheets used to modify the visual representation of RDF models represented as node-link diagrams. Possible modifications include changing the visual aspect of nodes and links (color, shape or icon, font, etc.), but also hiding parts of the graph or changing the layout of some elements. GSS draws many of its instructions from existing W3C Recommendations, namely, CSS and SVG. GSS features a cascading mechanism; its transformation model is loosely based on that of XSLT... the graph stylesheet is made of a set of rules. The left-hand side of a rule is called the selector, while the right-hand side is called the styling instruction set. Given the set of rules defined in a stylesheet (or several cascading stylesheets), the program in charge of styling RDF models (called a GSS engine) walks the entire graph, including resources, literals, and properties, and evaluates relevant rules on them. If the selector of a rule matches the current node (or arc) in the graph, the corresponding set of styling instructions is applied to the node or arc. Conflicts between rules matching the same node or arc are resolved, first, by giving higher priority to rules in the stylesheet applied last, and, second, to the most specific selector if both are in the same stylesheet... GSS stylesheets can be combined together with ease thanks to the cascading mechanism and the RDF language's capability to merge models. What we need now are stylesheets for all widely-used vocabularies..."

• [July 22, 2003] "XML Watch: Tracking Provenance of RDF Data. RDF Tools Are Beginning to Come of Age." By Edd Dumbill (Editor and publisher, xmlhack.com). In IBM DeveloperWorks (July 21, 2003). ['When you start aggregating data from around the Web, keeping track of where it came from is vital. In this article, Edd Dumbill looks into the contexts feature of the Redland Resource Description Format (RDF) application framework and creates an RDF Site Summary (RSS) 1.0 aggregator as a demonstration.'] "A year ago, I wrote a couple articles for developerWorks about the Friend-of-a-Friend (FOAF) project. FOAF is an XML/RDF vocabulary used to describe -- in computer-readable form -- the sort of personal information that you might normally put on a home Web page, such as your name, instant messenger nicknames, place of work, and so on... I demonstrated FOAFbot, a community support agent I wrote that aggregates people's FOAF files and answers questions about them. FOAFbot has the ability to record who said what about whom... The idea behind FOAFbot is that if you can verify that a fact is recorded by several different people (whom you trust), you are more likely to believe it to be true. Here's another use for tracking provenance of such metadata. One of the major abuses of search engines early on in their history was meta tag spamming. Web sites would put false metadata into their pages to boost their search engine ranking... I won't go into detail on the various security and trust mechanisms that will prevent this sort of semantic vandalism, but I will focus on the foundation that will make them possible: tracking provenance... To demonstrate, I'll show you how to use a simple RSS 1.0 document as test data. Recently I set up a weblog site where I force my opinions on the unsuspecting public... Though RSS feeds of weblogs and other Internet sites are interesting from a browse-around, ego-surfing perspective, I believe the real value of a project like this is likely to be within the enterprise. Organizations are excellent at generating vast flows of time-sequenced data. To take a simple example, URIs are allotted for things like customers or projects, then RSS flows of activity could be generated and aggregated. Such aggregated data could then be easily sliced and diced for whoever was interested. For instance, administrators might wish to find out what each worker has been doing, project managers might want the last three status updates, higher-level management might want a snapshot view of the entire department, and so on. It is not hard to imagine how customer relationship management (CRM) might prove to be an area where tools of this sort would yield great benefits... The simple example demonstrated in this article only scratches the surface of provenance tracking with RDF. On the Web, where information comes from is just as important as the information itself. Provenance-tracking RDF tools are just beginning to emerge, and as they become more widely used they will no doubt become more sophisticated in their abilities. The Redland RDF application framework is a toolkit that's definitely worth further investigation. It has interfaces to your favorite scripting language; it runs on UNIX, Windows, and Mac OS X..."

• [April 21, 2003] "Thinking XML: Introducing N-Triples. A Simpler Serialization for RDF." By Uche Ogbuji (Principal Consultant, Fourthought, Inc). From IBM developerWorks, XML zone. April 8, 2003. ['RDF/XML isn't the only representation of an RDF model. The W3C developed N-Triples, a format for an RDF representation that is especially suited for test suites. Here, Uche Ogbuji introduces N-Triples using examples converted from RDF/XML.'] "In an earlier article, I used the heading "Repeat after me: There is no syntax". RDF's traditional XML syntax is often maligned, but luckily it is not what makes RDF tick, and the emergence of alternative serializations has always been inevitable. One problem with XML as a serialization syntax is that it is so flexible that it can be difficult to compare desired versus actual results in the process of automated testing. Whether in regression testing or conformance testing, it is often useful to try to normalize XML to some form so that simple text comparisons give meaningful results. The XML community developed XML canonical form for such purposes, and the W3C RDF working group required the same sort of form for RDF while it was developing RDF conformance test suites. One option is to define a canonical form of RDF/XML that matches any graphs, and then canonicalize the resulting XML according to the relevant W3C recommendation. Instead, I think the RDF working group chose the right course in developing a simple and strictly-defined textual format for RDF graphs. This format is named N-Triples, and is incorporated into the RDF Test Cases working draft. In this article I introduce N-Triples, using examples converted from RDF/XML... I do not cover a few nuances; for example, a very strict set of characters is allowed in the syntax, and you must be careful to escape any characters outside these ranges. Some characters (in URI references) must be escaped using URI conventions, and others use an N-Triples convention with a leading backslash. If you are writing code to read or write N-Triples, be sure to see the specification for these details. One of several efforts aimed at a simple triples-based representation for RDF includes N3, which is pretty popular and is the source of some of the ideas in N-Triples. But N-Triples has the advantage of being written into a formal specification, and because of its use in the standard RDF test cases, will probably be implemented by all RDF processors..."

• [April 17, 2003] "Intellidimension Application Shows Power of RDF." By Jim Rapoza. In eWEEK (April 17, 2003). "Intellidimension Inc.'s RDF Gateway 1.0 is one of the first applications to address the use of the Resource Description Framework standard, which makes it possible to have metadata interoperate across Web sites and enable everything from powerful search agents to extensive cross-site agent applications. RDF is also the core technology behind the World Wide Web Consortium's semantic Web project, whose goal is to build a Web where the meaning of Web content is understandable to machines. However, adoption of RDF has been slow, especially when compared with XML, on which RDF is based. This is where RDF Gateway, released last month, comes in by providing a powerful server-based system for creating, deploying and managing RDF applications. In tests, eWEEK Labs used RDF Gateway to build a wide variety of Web applications that incorporated and understood RDF, providing a level of content interactivity that would be the envy of most enterprise portals and Web services. RDF Gateway runs as an all-in-one Web server, application server and database, with the database designed to handle RDF content. This works well and makes the product easy to deploy, but we would prefer a more modular approach that would make it possible, for example, to use the database in conjunction with another Web server and application server... The sample applications that Intellidimension provides on its site were a great help in developing for RDF Gateway. We especially liked the sample portal package, which made it possible to build a powerful, interactive information management portal with a slew of user customization options. This portal also showed how well RDF Gateway can make use of RSS (RDF Site Summary), probably one of the most common uses of RDF on the Web today. RSS is used by many Web sites to create summaries of their site content that can be easily used for syndication. With this application, it became easy for users to create customizable news sites by combing RSS feeds from a variety of Web and internal sources..."

• [March 07, 2003] "The Social Meaning of RDF." By Kendall Grant Clark. From XML.com (March 05, 2003). ['The W3C is about to undertake a discussion of what the social meaning of RDF is -- what the real world import is of an RDF statement. Kendall Clark previews the debate and recent related discussion.'] "RDF is frequently described as a tool for representing knowledge, but therein lies a hornet's nest of deeply conceptual questions, better left undisturbed if you can help it. Sometimes, however, the hornet's nest has to be overturned because it is necessary to address the deep conceptual questions directly. The formal blessing of RDF specifications, especially 'RDF Concepts and Abstract Syntax', is a case in point. In what remains of this column, I review some of the vigorous debate surrounding one troublesome section of this document, section 4... there remain significant issues to be resolved before RDF Concepts progresses in the W3C recommendation process. There are at least two different kinds of difficulty. First, these issues (knowledge representation, the relation of formal and social systems, the meaning of meaning, and so on) are simply very difficult. If they were easy, we would have had something like RDF a long time ago, or at the least there would be even more unemployed philosophers and logicians around. Second, these issues cut across areas internal to the institutional politics of the W3C and its constitutents..." See W3C Social Meaning Discussion - Agenda.

• [March 04, 2003] "Tip: Use 'rdf:about' and 'rdf:ID' Effectively in RDF/XML. Minimize Confusion in Specifying Resources." By Uche Ogbuji (Principal Consultant, Fourthought, Inc). From IBM developerWorks, XML zone. February 2003. ['The combination of RDF and XML allows for several different approaches to specifying resources, and sometimes the rules for interpreting the syntax can be troublesome. In this tip, Uche Ogbuji uses examples to illustrate the various behaviors of the rdf:ID and rdf:about attributes, and shows how to use XML Base to control these behaviors.'] "This tip covers the RDF/XML syntax specification of 23-January-2003. You may want to review the latest W3C RDF primer if you are not familiar with recent RDF specifications. In RDF/XML, the subjects of statements are organized into node elements, which use attributes such as rdf:about and rdf:ID to set the subject for a collection of statements about that subject. Rules govern how the actual RDF subject URIs are constructed from these attributes, but there is plenty of room for confusion, and even instability, in the parsing results from environment to environment, if you're not careful. This tip offers some practices that can help minimize such errors and confusion... The behavior of rdf:about with respect to relative URIs also applies to similar attributes such as rdf:resource. The behavior of rdf:ID is similar to that of rdf:bagID and the like. Throughout your RDF/XML files, you should be acutely aware of any base URIs that are in effect so you can be sure you understand the process by which the RDF model is generated. As for choosing between rdf:ID and rdf:about, you will most likely want to use the former if you are describing a resource that doesn't really have a meaningful location outside the RDF file that describes it. Perhaps it is a local or convenience record, or even a proxy for an abstraction or real-world object (although I recommend you take great care describing such things in RDF as it leads to all sorts of metaphysical confusion; I have a practice of only using RDF to describe records that are meaningful to a computer). So rdf:about is usually the way to go when you are referring to a resource with a globally well-known identifier or location..." See "RDF/XML Syntax Specification (Revised)." W3C Working Draft 23-January-2003 and the "RDF Primer," W3C Working Draft 23-January-2003.

• [February 12, 2003] "Building Metadata Applications with RDF." By Bob DuCharme. From XML.com (February 12, 2003). ['The Python RDFlib library gives Bob DuCharme a "lightbulb moment" with RDF.'] "The real test of any technology's value is what kinds of tasks are easier with it than without it. If I hear about some new technology, I'm not going to learn it and use it unless it saves me some trouble. Well, being a bit of a geek, I might play with it a bit, but I'm going to lose interest if I don't eventually see tangible proof that it either makes new things possible or old things easier. I've played with RDF for a while and found some parts interesting and other parts a mess. During this time, I continued to wonder what tasks would be easier with RDF than without it. I came across some answers (for example, various xml-dev postings or some documentation on the Mozilla project), but they usually addressed the issue in fairly abstract terms. The first time I tried the RDFLib Python libraries, the lightbulb finally flashed on. RDFLib lets you generate, store, and query RDF triples without requiring you to ever deal directly with the dreaded RDF/XML syntax. And you can do all this with a minimal knowledge of Python..."

• [February 07, 2003] "BrownSauce: An RDF Browser." By Damian Steer. From XML.com (February 05, 2003). ['One of RDF's problems, as Damian Steer points, is that it's rather easier to produce than it is to consume. So Damian set out to produce the nearest thing he could to a generalized RDF browser that would make a decent job out of displaying arbitrary RDF information.'] "BrownSauce [a SourceForge Project] is an RDF browser. It attempts, armed with no more than a knowledge of RDF and RDF Schema, to present all RDF data as intelligibly as possible. RDF is biased in favor of the data producer. Consumers may have to deal with all, some, or none of the expected properties or classes, and they may have to be aware that entirely unknown properties and classes are possible and legitimate. BrownSauce is an attempt to deal with all that is thrown at it... BrownSauce attempts to improve on the triples approach. The problem is that such a display is too fine grained, but it has advantages: it will work with large documents or even sources where no single document is available (e.g., databases). So how to can an application find the obvious patterns in RDF data? RDF, unlike XML, has no mechanisms for expressing data structure; indeed, it is a semi-structured data format, so such information would only be a partial help. Having said that, the reader may be aware of RDF Schema. Don't be fooled by the name: RDF Schemas describe properties and classes, but cannot state that 'Houses have addresses'... When one looks at RDF data it is apparent that there are regular patterns. These are captured in BrownSauce using a simple rule: start at a node and work outward, passing over blank nodes... Currently BrownSauce can only browse documents. From the outset, however, the plan was to extend browsing to other sources such as databases with web interfaces. The code is in place and may well be added in the near future..."

• [December 03, 2002] "RDF Update." By Shelley Powers. From XML.com. November 27, 2002. ['RDF has recently seen several new draft specifications released by the W3C. Shelley Powers, author of O'Reilly's upcoming book on RDF, has read through the new specs and reports on their highlights.'] "The W3C working group tasked to update and clarify the RDF specification recently released six new working drafts. The group is collecting comments, concerns, and corrections, which will be incorporated into the documents. At the end of November [2002], in preparation for submitting the documents for review as Candidate Recommendations, the working group will begin its final review... Rather than signalling an increase in complexity of the RDF specification, the documents actually clarify it, primarily by separating its different aspects instead of keeping them bundled together in a confusing jumble of syntax, concept, and semantics. Additionally, two of the documents were written with very specific goals in mind: the Test Cases document aids RDF tool developers; the RDF Primer provides an introduction to RDF which is less formal than the specification itself... In this article I examine the purpose and scope of each document. I also highlight some of the significant changes between these working drafts and the original release of the RDF specifications... Note: the RDF documents include [1] RDF Primer (W3C Working Draft 11 November 2002); [2] RDF Semantics (W3C Working Draft 12 November 2002); [3] RDF Vocabulary Description Language 1.0: RDF Schema (W3C Working Draft 12 November 2002); [4] RDF/XML Syntax Specification - Revised (W3C Working Draft 8 November 2002); [5] Resource Description Framework (RDF): Concepts and Abstract Syntax (W3C Working Draft 08 November 2002); [6] RDF Test Cases (W3C Working Draft 12 November 2002). See the W3C Resource Description Framework (RDF) website.

• [November 22, 2002] "RPV: Triples Made Plain." By Kendall Grant Clark. From XML.com November 20, 2002. ['In the XML community over the past week, the debate over RDF rumbles on. As just about the oldest application of XML and Namespaces, the fact that RDF is still a source of debate four years later is testament to both its significance and its troubles. Kendall Grant Clark, custodian of the XML-Deviant column's watchful eye over the XML community, brings us the latest developments in the debate. Tim Bray has responded to the RDF discussion with a suggestion for a new RDF/XML syntax that aims to answer some of the criticisms of the existing format.'] "... If you don't like or understand or prefer RDF's XML serialization, find a way to avoid dealing with it directly. Using an RDF triplestore from a high-level language is one such way, while retaining some, perhaps all of the benefits of RDF's data model. So, my argument is a more focused variant of the suggestion Shelley Powers has been making repeatedly on XML-DEV lately: if you don't like or understand or prefer RDF, just don't use it. This seems fair enough. Most recent discussion of RDF, which has bubbled over the bounds of XML-DEV and moved out into the broader confines of the Web development community, has been by turns absurd and sublime. From foundational debates about whether RDF is complex, or fights over how to characterize its complexity, to awfully redundant discussions about whether its XML serialization is all that user-unfriendly, to meta-debates in which various sides jockey for position to see which side can be described as unfair or 'politically correct' (whatever that could possibly mean in this context) or dismissive or narrow-minded or high-handed -- and on and on. Yet the debate has also been productive at times, including Tim Bray's RPV proposal ['The RPV (Resource/Property/Value) Syntax for RDF']. Bray says his RPV proposal 'is an XML-based language for expressing RDF assertions ... designed to be entirely unambiguous and highly human-readable.' That two-part design goal is worth spending some time with insofar as it's emblematic of a good deal of the underlying debate over RDF. To say that an XML language is or should be 'entirely unambiguous' and 'highly human-readable' is to say that it should be as easily digestible by machines as by humans. It's that tension which runs all the way from XML to RDF. Further, Bray suggests that RDF has failed to gain traction because of this tension: his RPV proposal 'is motivated by a belief that RDF's problems are rooted at least in part in its syntax.' He elaborates on this point by saying, first, that RDF's XML serialization is 'scrambled and arcane,' preventing people from easily reading or writing it; second, that the XML serialization uses qualified names in a way that's not user-friendly and is in some conflict with the TAG's idea that significant resources be identified by URI; third, that there doesn't seem to be a general problem for metadata folks to think of things in terms of RDF's 3-tuples; fourth, that some alternatives to RDF-XML, like n3, suffer because, as non-XML, they can't get the network effect of ubiquitous XML support; and, fifth, that the idea of embedding RDF in XML languages, which seemed in the summer of 2000, both to Leigh Dodds and much of the rest of the XML development community, like a viable approach, 'has failed resoundingly in the marketplace'..."

• [November 22, 2002] "The RPV (Resource/Property/Value) Syntax for RDF." By Tim Bray. November 2002. ['The RPV (Resource/Property/Value) syntax is an XML-based language for expressing RDF assertions. It is designed to be entirely unambiguous and highly human-readable.'] "The Resource Description Framework (RDF) is designed to facilitate the interchange and processing of metadata concerning Resources (where the word Resource is used in its Web sense). RDF models metadata as 3-tuples which assert that some resource has some property (identified by URI) which has a value identified either by URI or given literally. The centrality of metadata in many classes of application, and the simplicity and elegance of RDF's data model would seem to make it something that has many obvious applications on the Web. Despite this, RDF has been slow to catch hold. The RPV language proposal is motivated by a belief that RDF's problems are rooted at least in part in its syntax. Specifically: (1) The syntax of RDF/XML is sufficiently scrambled and arcane that it is neither human-writeable nor human-readable. (2) The RDF/XML syntax makes heavy use of qnames that is neither intuitive to humans nor conforms particularly well to Web Architecture, which requires that everything significant be identified by URI. (3) People who care about metadata have no trouble thinking in terms of resource/property/value triples. (4) Alternatives like N3 that make the RDF triples evident in syntax suffer in comparison to the XML/RDF syntax because they lack XML's widely-deployed base of software, i18n facilities, and APIs. (5) The notion that you RDF can be mixed into XML transparently enough to be unobtrusive has failed resoundingly in the marketplace..." See John Cowan's summary: "Mini-review of Tim Bray's RPV syntax for RDF. This is mostly a remapping of a small subset of standard RDF/XML. It has the following features that RDF/XML has not: (1) Expresses property names as URIs rather than QNames; (2) String-valued property can have the string stored remotely, reachable by URL; (3) Incorporates xml:base; (4) Provides separate base attributes for resources, properties, and values..."

• [November 15, 2002] "RDF, What's It Good For?" By Kendall Grant Clark. From XML.com. November 13, 2002. ['Kendall Clark's been keeping an eye on the XML-DEV debate and the subject of the spec everyone loves to hate, RDF. Bob DuCharme and John Cowan's recent XML.com article on RDF spawned discussion about what RDF was actually good for.'] "The Resource Description Framework is still among the most interesting of W3C technologies. But it's got persistent troubles, including having had its reputation beaten up unfairly as a result of the many and often nasty fights about RSS. But, just like my eccentric old uncle, RDF is not entirely blameless. In a previous XML-Deviant article ('Go Tell It On the Mountain') I argued that RDF's trouble might have something to do with it having been the victim of poor technical evangelism. In some sense that's still true. Recently I googled for a comprehensive, up-to-date RDF tutorial, which proved as elusive as finding Uncle's dentures the morning after nickel beer night at the bingo hall. In fact, I was hard pressed to find an RDF tutorial which looked like it had been updated this year. And one which I did find simply listed 13 different ways to express the same basic set of assertions, which not only makes a terrible tutorial, but also exemplifies another of RDF's persistent troubles: its XML serialization... During the time I've tracked RDF in the XML community, I can't recall running across even one enthusiastic defender of RDF's XML serialization. Apparently everyone, or so it seems, thinks it's a nasty kludge at best. Now, I've been using RDF in some of my recent Python programming, using Daniel Krech's excellent rdflib -- which, as Andrew Kuchling reminded me, thanks to its new ZODB/ZEO storage layer, now does fully-distributed storage. One virtue of rdflib is that it shields me, the carefree application hacker, from having to deal with RDF's XML serialization. I never think about it or about its warts. I rarely even see it. Which is perfect. As long as, when I send the XML-serialized dump of my RDF triple store to someone else, they end up with the same graph of assertions, I'm happy. But everyone's needs are not as easy to satisfy..."

• [November 08, 2002] "Make Your XML RDF-Friendly." By Bob DuCharme and John Cowan. From XML.com. October 30, 2002. ['The describe how to structure XML documents so that they can be used by RDF processors. The authors explain: "as RDF interest and application development grows, there's an increasing payoff in keeping RDF concerns in mind along with the other best practices as you design document types".'] "Suppose you're designing an XML application or maybe just writing a DTD or schema. You've followed various best practices about element and attribute names, when to use elements versus attributes, and other design issues, because you want your XML to be useful in the widest variety of situations. As RDF interest and application development grows, there's an increasing payoff in keeping RDF concerns in mind along with the other best practices as you design document types. Your documents store information, and small tweaks to their structure can allow an RDF processor to see that information as subject-predicate-object triples, which it can make good use of. Making your documents more 'RDF-friendly' -- that is, more easily digestible by RDF applications -- broadens the range of applications that can use your documents, thereby increasing their value. A lot of XML RDF documents look like they were designed purely for RDF applications, but that's not always the case. The frequent verbosity of RDF XML, which often intimidates RDF beginners, is a by-product of the flexibility that makes RDF easy to incorporate into your existing XML. By observing eight guidelines when designing a DTD or schema, you can use this flexibility to help your documents work with RDF applications as well as non-RDF applications. Some of the guidelines are easy, while some involve making choices based on trade-offs. But knowing what the issues are gives you a better perspective on the best ways to model your data... As RDF tools become more widely available and easy to use, you'll have more resources available to do improved metadata management for your own data. Even if you're not ready to build serious RDF applications just yet, making more of your own data RDF-friendly will do more than widen the number of applications that can use it. For many people, the kinds of things that RDF is good at become clearer to them when used with data that is important to their business or important to them personally, such as an address or appointment file. Using RDF tools to play with your own data will help you understand the strong points of RDF and, perhaps, even the strong points of your own data better..." See W3C Resource Description Framework (RDF) website and Semantic Web Activity Statement.

• [May 17, 2002] "Go Tell It On the Mountain. [RDF Primer]". By Kendall Grant Clark. From XML.com. May 15, 2002. ['As part of the re-framing of the W3C's Resource Description Framework a primer has been produced to accompany the new RDF specifications. Kendall Clark reviews the new document.'] On RDF Primer, W3C Working Draft 26 April 2002. "... After languishing for a relatively long time, the next 12 to 18 months is a make or break time for RDF, as well as for the Semantic Web Activity, of which it is a crucial element. Despite the technical problems with RDF, the biggest impediment to its widespread use to date has been the failure of evangelism, not so much because it was done poorly, though there have been missteps, but, rather, because it was mostly not done at all. And so the arrival of a Primer among the work product of the RDF Core WG is a happy occasion. It offers those of us not serving on an RDF working group, but inclined to do formal or informal evangelization of RDF among our peers, a non-normative but still blessed and trusted ground upon which to base our efforts. As well, it offers curious, potential users a more easily accessible introduction to RDF, and that can only be a good thing. There is some sense in which there being an RDF primer is far more strategically valuable than the sort of primer it is. However, as with other introductory texts, which are often the only texts about a technology users ever read, there are certain principles it is hard to quarrel with. Among these are simplicity and concision. In what ways and to what extent these principles are met, as always, at least partially a subjective question. I for one think that the RDF Primer gets more things right than it gets wrong, but I'm also hopeful that future drafts grow increasingly simplified and concise..."

• [April 2002] "Ontology Storage and Querying." By Aimilia Magkanaraki, Grigoris Karvounarakis, Ta Tuan Anh, Vassilis Christophides, and Dimitris Plexousakis. Foundation for Research and Technology Hellas, Institute of Computer Science Information Systems Laboratory. Technical Report No 308. April 2002. 21 pages. Review of RDF tools and APIs. [*NB: "One of the conclusions drawn from this survey is that the majority of the query languages do not yet support the complete set of modeling constructs offered by the above standards. Furthermore, the frontiers between querying and inferring capabilities offered by these languages are not clear. In most cases, inference is limited to a recursive traversal of ontology class/property hierarchies as well as of data paths involving transitive properties. We believe that the target functionality of the proposed query languages still has to be justified with respect to real large-scale Semantic Web applications."] "The necessity for ontology building, annotating, integrating and learning tools is uncontested. However, the sole representation of knowledge and information is not enough. Human information consumers and web agents have to use and query ontologies and the resources committed to them, thus the need for ontology storage and querying tools arises. However, the context of storing and querying knowledge has changed due to the wide acceptance and use of the Web as a platform for communicating knowledge. New languages for querying (meta)data based on web standards (e.g., XML, RDF, Topic Maps) have emerged to enable the acquisition of knowledge from dispersed information sources, while the traditional database storage techniques have been adapted to deal with the peculiarities of the (semi)structured data on the web. The purpose of this chapter is to briefly present and evaluate a set of query languages and associated tools for ontology/resource storage and querying aiming to support large-scale Semantic Web applications, the next evolution step of the Web. This list of languages and tools is by no means complete and the tools presented are indicative of the tendency to provide full storage and query support to web-based ontology/metadata standards, such as RDF, RDFS, Topic Maps, DAML+OIL or the forthcoming Web Ontology Language. Our work in this chapter focuses on the evaluation of querying languages designed for Semantic Web related knowledge representation formalisms rather than general-purpose querying languages (e.g., SQL, Datalog, F-logic). Although it has to be proven in practice, RDF-enabled search technologies have the potential to provide a significant improvement over the current keyword-based engines or theme navigation search, especially when it comes to conceptual browsing and querying. Furthermore, this orientation facilitates the comparison of querying languages and tools, since it provides a common reference base. It should be stressed that our comparison of ontology query languages and tools does not rely on performance figures, since these would require extensive comparative experiments, which go beyond the scope of this work. On the contrary, we present an overview of general system features and query language expressiveness, while providing the interested reader with useful references to additional informative material..." [cache]

• [April 06, 2002] "Managing structured Web service metadata. The realities of managing Web service metadata." By Uche Ogbuji (Principal Consultant, Fourthought, Inc.). From IBM developerWorks, Web services. April 2002. ['This article builds on an earlier developerWorks article on using the Resource Description Framework (RDF) to enhance WSDL, and related to a recent article on using SOAP with RDF. Uche Ogbuji looks at how updates in WSDL affect the techniques presented earlier, and draws on the significant discussion of RDF and Web services description to show how developers can use both to their advantage.'] "About a year and a half ago, I took a close look of how the then just announced Web Services Description Language (WSDL) could benefit from interacting with Web metadata format, RDF, either at the standards level, or at the level of individual developer effort. Since then, there has been a huge amount of activity in the Web services community and in the RDF (and Semantic web) community. Some of this has been very good, as dialog between these groups has taken root, and the technologies put forth by both groups have been improved. Some has also been bad, as the press has somehow conjured up a fantastical struggle between Web services camps and Semantic Web camps at the W3C, fighting for the resources of the consortium. All these developments are a great insight into the development and interaction of next-generation technologies, but in this article, I shall distill the most important developments of interest to developers... The recent RDF model theory and RDF/XML syntax specifications motivate some changes to the approach I have taken for mapping from WSDL to RDF. Other factors have also weighed in. In particular, Eric Prud'hommeaux has worked to improve on my approach by trying to make a mapping of the underlying intent behind the WSDL elements, rather than my own mechanical approach to the mapping. Certainly such a mapping would be more useful for general RDF integration, and one hopes that it is such a rich mapping that it will be accepted by the Web services description working group. I, however, also had a particular aim in my own approach: to provide a mapping straightforward enough to be palatable for non-RDF-types, and as close as possible to an identity transform from XML. With the increasing cooperation between the Web services and RDF camps, such a mechanical mapping is no longer a great necessity, so I shall look a bit more at the big picture for developers... developments in Web services and RDF provide not only richer tools for developer looking to take advantage of both, but a greater spirit of cooperation between the two efforts. The RDF query of WSDL metadata that I demonstrated can easily enough be duplicated using SQL queries, or API calls against some data binding of WSDL, but the benefit of using RDF is that one can then mix WSDL with other important RDF-based metadata, including content description and syndication formats (for example, Prism and RSS), privacy profiles (for example, P3P), and other emerging RDF applications. The more generic the management of Web services information, the more readily productivity output can be enhanced by improved integration..."

• [March 21, 2002]   W3C RDF Core Working Group Publishes RDF Primer Working Draft.    The W3C RDF Core Working Group has produced an initial public working draft RDF Primer. The Resource Description Framework (RDF) is a general-purpose language for representing information in the World Wide Web. It is particularly intended for representing metadata about Web resources, such as the title, author, and modification date of a Web page, the copyright and syndication information about a Web document, the availability schedule for some shared resource, or the description of a Web user's preferences for information delivery. RDF provides a common framework for expressing this information in such a way that it can be exchanged between applications without loss of meaning. Since it is a common framework, application designers can leverage the availability of common RDF parsers and processing tools. Exchanging information between different applications means that the information may be made available to applications other than those for which it was originally created. This Primer is designed to provide the reader the basic fundamentals required to effectively use RDF in their particular applications." [Full context]

• [March 11, 2002] "Using RDF with SOAP. Beyond Remote Procedure Calls." By Uche Ogbuji (Principal Consultant, Fourthought, Inc.). From IBM developerWorks, Web services. February 2002. ['This article examines ways that SOAP can be used to communicate information in RDF models. It discusses ways of translating the fundamental data in RDF models to the SOAP encoding for PC-like exchange, or for directly passing parts of the model in RDF/XML serialized form.'] "SOAP is a transport protocol for carrying XML payloads over lower level Internet protocols. Specifications of the transport prior to 1.2 built in a suggested encoding of XML that is geared towards the serialization of programming language constructs. Such encodings are the staple of what is known as remote procedure call (RPC) systems, which have the common aim of making requests to remote computers look just like local procedure invokations. Other examples of RPC encodings are External Data Representation (XDR), from 'classic' RPC (and defined in RFC 1014), and Common Data Representation (CDR) from CORBA. As a result of bundling an encoding with such relatives, SOAP took on a decidedly application-programming feel, and its usefulness for general data exchange seemed suspect. These early flavors of SOAP generated much controversy. Firstly, mixing transport and data encoding specifications seems to be a very messy approach to communications, and seems to fly in the face of layered protocols that have been the practice in networking for decades. After all, the specification for HTML mark-up is not embedded into the HTTP specification. Secondly, choosing an RPC-like encoding for pre-eminence puts SOAP in an odd spot; it has little more expressive power than pre-XML RPC mechanisms, yet it is practically guaranteed to be less efficient because of XML's verbosity and the more generic architectures of HTTP, SMTP, and the like. It would seem that the only advantage SOAP brought as a next-generation RPC was to unify the Microsoft and CORBA camps; this is important, but certainly not what SOAP appeared to be promising. One important down-side consequence of SOAP-as-RPC is that such a system is completely unsuitable for the next-generation-EDI ambitions of Web services in general. If Web services are to become the new way businesses communicate over networks, they would seem to need a transport mechanism that communicates at the level of business and legal requests, rather than at the level of programming language APIs. And surely enough, the ebXML initiative, whose ambition is to use XML to craft a system for international electronic business communication, originally balked at using SOAP, as did a few other influential organizations... There are other approaches and ideas when it comes to how SOAP and RDF can inter-operate, and indeed it is a topic of constant interest as RDF users discover Web services and vice versa... Certainly more generic systems for serializing XML-based data will only enrich the world Web services." Also in PDF format.

• [January 11, 2002] "RDF Declarative Description (RDD): A Language for Metadata." By Chutiporn Anutariya, Vilas Wuwongse, Kiyoshi Akama, and Ekawit Nantajeewarawat. In Journal of Digital Information [ISSN: 1368-7506](January 2002). Metadata: Papers from the Dublin Core 2001 Conference. "RDF Declarative Description (RDD) is a metadata modeling language which extends RDF(S) expressiveness by provision of generic means for succinct and uniform representation of metadata, their relationships, rules and axioms. Through its expressive mechanism, RDD can directly represent all RDF-based languages such as OIL and DAML-family markup languages (e.g., DAML+OIL and DAML-S), and hence allows their intended meanings to be determined directly without employment of other formalisms. Therefore, RDD readily enables interchangeability, interoperability as well as integrability of metadata applications, developed independently by different communities and exploiting different schemas and languages. Moreover, RDD is also equipped with computation and query-processing mechanisms." Full article available in PDF format. [cache]

• [January 04, 2002] "RQL: A Declarative Query Language for RDF." By Greg Karvounarakis, Vassilis Christophides, and Dimitris Plexousakis (Institute of Computer Science, FORTH; Heraklion, Greece). In D-Lib Magazine Volume 7 Number 12 (December 2001). ISSN: 1082-9873. "In the next evolution step of the Web, termed the Semantic Web, vast amounts of information resources (i.e., data, documents, programs) will be made available along with various kinds of descriptive information (i.e., metadata). This evolution opens new perspectives for Digital Libraries (DLs). Community Web Portals, E-Marketplaces, etc. can be viewed as the next generation of DLs in the Semantic Web era. Better knowledge about the meaning, usage, accessibility or quality of web resources will considerably facilitate automated processing of available Web content/services. The Resource Description Framework (RDF), enables the creation and exchange of resource metadata as any other Web data. To interpret metadata within or across user communities, RDF allows the definition of appropriate schema vocabularies (RDFS). The most distinctive feature of the RDF model is its ability to superimpose several descriptions for the same Web resources in a variety of application contexts (e.g., advertisements, recommendations, copyrights, content ratings, push channels, etc.), using different DL schemas (many of which are already expressed in RDF/RDFS. See examples. Yet, declarative languages for smoothly querying both RDF resource descriptions and related schemas, are still missing... This ability is particularly useful for next generation DLs that require the management of voluminous RDF description bases, and can provide the foundation for semantic interoperability between DLs. For instance, in knowledge-intensive Web Portals, various information resources such as sites, articles, etc. are aggregated and classified under large hierarchies of thematic categories or topics. These descriptions are exploited by push channels aiming at personalizing Portal access (e.g., on a specific theme), using standards like the RDF Site Summary... Motivated by the above issues, we have designed RQL, a declarative query language for RDF descriptions and schemas. RQL is a typed language, following a functional approach (as in ODMG OQL or W3C XQuery). RQL relies on a formal graph model (as opposed to other triple-based RDF query languages) that captures the RDF modeling primitives and permits the interpretation of superimposed resource descriptions by means of one or more schemas..."

• [January 04, 2002] "Doubt Cast Over Web Standard's Ownership." By Margaret Kane. In CNet News.com (January 3, 2002). "A Canadian company is claiming that a popular Web technology infringes on a patent it owns. The technology in question, Resource Description Framework, is based on Extensible Markup Language (XML) and allows programmers to write software to access Web resources, such as Web page content, music files and digital photos. The RDF standard has been endorsed by the World Wide Web Consortium, which evaluates and recommends standards for Web technologies. Vancouver-based UFIL Unified Data Technologies, a private company, claims that it owns U.S. patent 5,684,985, a "method and apparatus utilizing bond identifiers executed upon accessing of an endo-dynamic information node." The patent was awarded in November 1997. UFIL is working with Toronto-based Patent Enforcement and Royalties Ltd. (PEARL) to enforce the claims. According to press releases on PEARL's Web site, the companies believe as many as 45 companies may be infringing on the patents... The patent may also infringe on the RDF Site Summary standard, a way to describe Web content that's written in something other than HTML. RSS lets Web sites exchange information about Web site content and e-commerce data, for instance. RSS was originally developed by Netscape Communications, now owned by AOL Time Warner. Netscape's Mozilla browser uses the technology, as do other programs. Daniel Weitzner, technology and society domain leader at the W3C, said the consortium has not been approached directly regarding the patent issue..." See "Resource Description Framework (RDF)" and "RDF Site Summary (RSS)."

• [September 28, 2001] "RDF/Topic Maps: late/lazy reification vs. early/preemptive reification." By Steven R. Newcomb. Posting 2001-09-27. "For me, at least, the shortest, most compelling and cogent demonstration of a certain critical difference between Topic Maps and RDF was Michael Sperberg-McQueen's wrap-up keynote at the Extreme Markup Languages Conference (www.extrememarkup.com) last August. Michael brought colored ribbons and other paraphernalia to the podium, in order to illustrate his words... In the past, I myself have considered RDF as the competitor of Topic Maps. Happily, I was wrong -- at least in fundamental technical terms. Indeed, I now believe that if there were no RDF, the Topic Maps camp would have to invent something like it in order to make the Maps paradigm predictably comprehensible by the programmers who are pioneering the development of the Internet. There are other interesting comparisons to be made between RDF and Topic Maps, but ever since Michael's demonstration of the difference between early vs. late (preemptive vs. lazy) reification, I have been meaning to document both the difference and the demonstration..." See also "(XML) Topic Maps."

• [August 24, 2001] "On the Integration of Topic Maps and RDF Data." By Martin Lacher and Stefan Decker. 14 pages. Paper presented "on the integration of Topic Maps and RDF" at the August 2001 'Semantic Web Workshop' at Stanford. ['We provide a way to make Topic Map sources RDF-queriable by exchanging one layer in a layered data model stack. The exchanged layer is the layer on which both are represented as a graph; we use TMPM4 as a Topic Map graph representation. Our approach complies with what Graham Moore has termed in his XML Europe paper "modeling the model".'] "Topic Maps and RDF are two independently developed paradigms and standards for the representation, interchange, and exploitation of model-based data on the web. Each paradigm has established its own user communities. Each of the standards allows data to be represented as a graph with nodes and labeled arcs which can be serialized in one or more XML- or SGML-based syntaxes. However, the two data models have significant conceptual differences. A central goal of both paradigms is to define an interchangeable format for the exchange of knowledge on the Web. In order to prevent a partition of the Web into collections of incompatible resources, it is reasonable to seek ways for integration of Topic Maps with RDF. A first step is made by representing Topic Map information as RDF information and thus allowing Topic Map information to be queried by an RDF-aware infrastructure. To achieve this goal, we map a Topic Map graph model to the RDF graph model. All information from the Topic Map is preserved, such that the mapping is reversible. The mapping is performed by modeling the graph features of a Topic Map graph model with an RDF graph. The result of the mapping is an RDF-based internal representation of Topic Maps data that can be queried as an RDF source by an RDF-aware query processor... Interoperability is of greatest importance for the future Semantic Web. We suggested a way to achieve interoperability between Topic Maps and RDF, which enables the joint querying of RDF and Topic Maps information sources. Our work builds on existing work on general approaches for the integration of model based information resources. In contrast to those general approaches we showed a detailed mapping specifically from XTM Topic Maps to RDF. We achieved this by adopting an internal graph representation for Topic Maps, which has been published as part of one of the processing models for Topic Maps. We perform a graph transformation to generate an RDF graph from the Topic Map graph representation. The Topic Map source can now be queried with an RDF query language together with RDF information sources. We see this as a first step towards the integration of the many heterogeneous information sources available on the Web today and in the future." [cache]

• [July 17, 2001]   Proposal for Basic Semantic Web Language (BSWL).    Sean B. Palmer has announced a new proposal for a stripped down RDF-in-XML syntax called "BSWL" or the "Basic Semantic Web Language." The abstract syntax of this proposed language "is indeed very simple, consisting only of a set of three elements and a handful of attributes. The elements are: (1) <t> , denoting a triple; (2) <po>, denoting a predicate an object pair; (3) and <o>, denoting an object. Each of these elements has a range of attributes that associate a URI with a particular part of the content..." The proposed syntax features advantages over RDF M&S [Resource Description Framework (RDF) Model and Syntax Specification], including: "(1) Simpler syntax - no typed or anonymous nodes, allows one to form triples simply by nesting QNames; (2) Has a special syntax for referring to XML QNames; (3) Forces you to use xml:lang as part of the model, so it isn't lost; (4) Allows you to nest triples so that the subject of the former triple becomes the object of the latter triple; (5) Is possible to convert back into RDF M&S, and vice versa -- once RDF Core decide what to do about anonymous nodes; (6) Files using abbreviated BSWL tend to be shorter than RDF M&S." [Full context]

• [July 13, 2001] "Matching RDF Graphs." By Jeremy Carroll (HP Labs). July 13, 2001 (draft). "The Resource Description Framework (RDF) describes graphs of statements about resources. This paper explores the equality of two RDF graphs in light of graph isomorphism literature. We consider anonymous resources as unlabelled vertices in a graph, and show that the standard graph isomorphism algorithms, developed in the 1970s, can be used effectively for comparing RDF graphs..." [Post to 'www-rdf-interest@w3.org': "One of the improvements in Jena-1-1-0 [http://www-uk.hpl.hp.com/people/bwm/rdf/jena/] is a matching algorithm that can tell if two models are the same. The algorithm aligns the anonymous resources; so that two files, identical except for the order of statements will compare equal. I've written up the algorithm used... It's based on a standard algorithm from graph theory. It could also be useful for deeper notions of equivalence (e.g. after we have decided that certain pairs of URI's actually refer to the same resource). Any feedback, including stuff like typos and spelling errors, as well as more profound comments, would be welcome. I plan to take the doc to a second final version in three weeks time, when I will post a technical report number and a non-transitory URL..." [cache]

• [July 05, 2001] "Basic XML and RDF Techniques for Knowledge Management. Part 1: Generate RDF using XSLT. [Thinking XML #4.]" By Uche Ogbuji (CEO and principal consultant, Fourthought, Inc.). From IBM developerWorks. July 2001. ['I've started a series in my column about working with RDF in an XML system. I use an issue tracker as my example: hopefully one that will soon be the live tracker of RIL, 4Suite, etc... Columnist Uche Ogbuji begins his practical exploration of knowledge management with XML by illustrating techniques for populating Resource Description Framework (RDF) models with data from existing XML formats. As shown in the three code listings, RDF can be used as a companion to customized XML, not just as a canonical representation for certain types of data. This column, with code samples included, demonstrates how easy it can be to jump-start knowledge management with RDF even relatively late in the development game.'] "Although Resource Description Framework (RDF) was designed by the W3C as a general metadata modeling facility, it offers many features that make it an ideal companion to XML data. In many emerging XML applications, the knowledge encapsulated in the application throughout its lifetime is stored in XML documents in a database or repository. The basis of RDF's strength as a knowledge-management tool is that it allows you to organize, interrelate, classify, and annotate this knowledge, thereby increasing the aggregate value of the stored data. RDF has a reputation for complexity that is belied by the simplicity of adding RDF support to XML-based applications. This article begins an exploration of the symbiosis between RDF and XML. I'll demonstrate how to use XSLT to generate RDF from XML... In this column I have presented a simple example of the use of XSLT to extract RDF from XML instances. As more and more XML-based applications come into use, such techniques are useful in expanding applications with knowledge-management features. The next installment will continue with the issue tracker example, demonstrating batch processing of the issue documents and some open-source tools useful for such processing." Article also available in PDF format.

• [June 20, 2001] "Simplified XML Syntax for RDF." By Jonathan Borden (Tufts University School of Medicine, The Open Healthcare Group). June 17, 2001 or later. "A simplified XML syntax for RDF is proposed. Its major differences with RDF 1.0 are: (1) namespace = http://www.openhealth.org/RDF/RDFSurfaceSyntax; (2) defined as tree regular expression; (3) attribute aboutQ="ex:name" accepts QName as value indicating subject; (4) attribute resourceQ="ex:value" accepts QName as value indicating object; (5) rdf:parseType="Resource" is default; (6) The subject or object of a statement may be either a URI reference, a qualified name, a quantified variable, another statement or a collection of statements; (7) ?x defines a quantified variable. XML Syntax: The XML syntax for RDF 1.0 can be described in terms of a tree regular expression. This form can be thought of as expressing constraints on the XML Infoset which arises when parsing an RDF document. The advantage of expressing the syntax in this form over EBNF, is that a tree regular expression (e.g., RELAXNG/TREX schema http://relaxng.org) already takes into account the rules of XML syntax + XML namespaces, e.g., correctly handles namespace prefixes, empty elements, mixed content, whitespace, attribute ordering etc. Such schemata are also described as 'hedge regular expressions' or 'hedge automata' [http://www.oasis-open.org/cover/hedgeAutomata.html]. The tree regular expression schema for RDF 1.0 is available [online]. This schema handles several proposed updates such as the requirement that the "rdf:about" and "rdf:ID" attributes be prefixed/qualified. A tree regular expression for the proposed syntax is available [online]..." See: "RELAX NG."

• [June 20, 2001] "Making RDF Syntax Clear. Proposal of a DTD and minor syntax enhancement to RDF, to overcome many of the current practical difficulties." By Rick Jelliffe (Topologi Pty. Ltd.) 2001-06-20. "The current RDF Recommendation is almost impossible to implement because the discipline of a DTD was not used. Consequently, RDF implementations lack exchangability, and most people coming to the RDF Spec (from outside the 'RDF Community') expecting clear description of syntax must go away disappointed/ Furthermore, the advent of RDFS raises compatability issues, in that certain elements are used in RDFS, but are only general names in RDF. This proposal suggests the the situation could be improved by: [1] creating a normative DTD for RDF; [2] state clearly that this DTD (and DTDs that use it) embodies the RDF exchange current RDF exchange XML; [3] reconciles the use of namespaces in RDF with XML Schemas; [4] clarifies RDF's current syntax with standard concepts such as "architectures". I propose that this DTD should be included as a normative part of the RDF specification, and the BNF sections removed or reworded to fit in with it. From the 2001-06-20 posting to 'www-rdf-interest@w3.org': "I have posted to the RDF comments list a proposal for clarifying RDF syntax. This proposal features a new DTD, used to map between RDF documents and a notional XML Schemas schema using xsi:type. I have been working through RDF specifications and examples again recently, and I am even more convinced than ever that getting the basic discipline of the transfer syntax clear is a prerequisite for RDF becoming useful..."

• [May 24, 2001] "Using the Jena API to Process RDF. [Tutorial.] By Joe Verzulli. From XML.com. May 23, 2001. ['Jena is a freely-available Java API for processing RDF. This article provides an introduction to the API and its implementation.'] "There has been growing interest in the Resource Description Framework (RDF) and a number of tools and libraries have been developed for processing it. This article describes one such library, Jena, a Java API for processing RDF. It is also the name of an open source implementation of the API.'] XML is very flexible and allows information to be encoded in many different ways. If meaningful tag names are used it is relatively easy for a person to determine the intended interpretation of an XML string. However, it is difficult for programs to determine the intended interpretation since programs don't understand English tag names. DTDs and XML Schemas don't really help in this regard. They just allow a program to verify that XML strings conform to some set of rules. RDF is a model and XML syntax for representing information in a way that allows programs to understand the intended meaning. It's built on the concept of a statement, a triple of the form {predicate, subject, object}. The interpretation of a triple is that <subject> has a property <predicate> whose value is <object>... RDF requires that different kinds of semantic information (e.g., subjects, properties, and values) be placed in prescribed locations in XML. Programs that read an XML encoding of RDF can then tell whether a particular element or attribute refers to a subject, a property, or the value of a property. Jena was developed by Brian McBride of Hewlett-Packard and is derived from earlier work on the SiRPAC API. Jena allows one to parse, create, and search RDF models. Jena defines a number of interfaces for accessing and manipulating RDF statements..." [Website description: "Jena is an experimental java API for manipulating RDF models. Its features include: (1)statement centric methods for manipulating an RDF model as a set of RDF triples (2) resource centric methods for manipulating an RDF model as a set of resources with properties (3) cascading method calls for more convenient programming (4) built in support for RDF containers - bag, alt and seq (5) enhanced resources - the application can extend the behaviour of resources (6) mulptiple implementations (7) integrated parser (David Megginson's RDFFilter). An alpha quality implementation is available for download."]

• [May 23, 2001] "RDF and TopicMaps: An Exercise in Convergence." By Graham Moore (Vice President Research & Development, Empolis GmbH). Paper for XML Europe 2001 Berlin. 2001-05-24. ['This paper presents: (1) a way in which RDF can be used to model topicmaps and vice versa; (2) the issues that arise when performing a model to model mapping; (3) some proposals for changes to XTM to enable semantic interchange of the two standards. I am presenting this paper on Thursday at XML Europe if anyone is around and interested. I don't think this is the complete solution to the integration issue. However, I think that this paper could help focus some of the discussions.'] "There has long been a sense in the semantic web community that there is a synergy between the work of ISO and TopicMaps.org on TopicMaps and that of the W3C on RDF. This paper looks at why and how we can bring these models together to provide a harmonised platform on which to build the semantic web. The reasoning behind bringing together these two standards is in the fact that both models are intent on describing relationships between entities with identity. The question we look to answer in this paper is 'Is the nature of the relationships and the identified entities the same'. If we can show this to be true then we will be able to have a common model that can be accessed as a TopicMap or as a RDF Model. To make this clearer, if we have a knowledge tool X we would expect to be able to import some XTM syntax, some RDF syntax and then run either a RDF or TMQL query in the space of tool X and expect sensible results back across the harmonised model. In order to achieve this aim we need to show a model to model mapping between the two standards. We present the TopicMap m