W3C has announced the release of five Last Call Working Draft specifications for the OWL Web Ontology Language Version 1.0, together with an updated Test Cases document. OWL "is used to publish and share sets of terms called ontologies, providing advanced Web search, software agents and knowledge management. It is intended to provide a language that can be used to describe the classes and relations between them that are inherent in Web documents and applications. The Web Ontology Language OWL is a semantic markup language for publishing and sharing ontologies on the World Wide Web. OWL is developed as a vocabulary extension of RDF (the Resource Description Framework) and is derived from the DAML+OIL Web Ontology Language." According to WG Co-Chair Jim Hendler, the W3C working group has made a best effort attempt to address all comments received to date, and now seeks confirmation that the comments have been addressed to the satisfaction of the user community, allowing the WG to move forward with Proposed Recommendations following the Last Call process. Comments are due by May 9, 2003.

OWL Web Ontology Language [Last Call] Documents

Five of the recently published Web Ontology Language Working Draft documents are 'Last Call'; the Test Cases are still under development.

1. OWL Web Ontology Language Overview. Edited by Deborah L. McGuinness (Knowledge Systems Laboratory, Stanford University) and Frank van Harmelen (Vrije Universiteit, Amsterdam). This version URL: http://www.w3.org/TR/2003/WD-owl-features-20030331/. Latest version URL: http://www.w3.org/TR/owl-features/. W3C Working Draft 31-March-2003. "The OWL Web Ontology Language is designed for use by applications that need to process the content of information instead of just presenting information to humans. OWL facilitates greater machine readability of Web content than that supported by XML, RDF, and RDF Schema by providing additional vocabulary along with a formal semantics. OWL has three increasingly-expressive sublanguages: OWL Lite, OWL DL, and OWL Full. This document is written for readers who want a first impression of the capabilities of OWL. It provides an introduction to OWL by informally describing the features of each of the sublanguages of OWL. Some knowledge of RDF Schema is useful for understanding this document, but not essential. After this document, interested readers may turn to the OWL Guide for a more detailed descriptions and extensive examples on the features of OWL. The normative formal definition of OWL can be found in the OWL Semantics and Abstract Syntax..."

2. OWL Web Ontology Language Reference. Edited by Mike Dean and Guus Schreiber. Authors: Frank van Harmelen, Jim Hendler, Ian Horrocks, Deborah L. McGuinness, Peter F. Patel-Schneider, and Lynn Andrea Stein. W3C Working Draft 31-March-2003. This version URL: http://www.w3.org/TR/2003/WD-owl-ref-20030331/. Latest version URL: http://www.w3.org/TR/owl-ref/. "This document gives a systematic, compact and informative description of all the modelling primitives of OWL, using the RDF/XML exchange syntax for OWL. We expect this document to serve as a reference guide for users of the OWL language. Readers unfamiliar with OWL may wish to first consult the OWL Overview document, and subsequently the OWL Guide for a more narrative description and examples of the use of the language. This document assumes the reader is familiar with the basic concepts of RDF and has a working knowledge of the RDF/XML syntax and of RDF Schema. The normative reference on the precise syntax of the OWL language constructs can be found in the OWL Semantics and Abstract Syntax document. This document also contains a precise definition of the meaning of the language constructs in the form of a model-theoretic semantics..."

3. OWL Web Ontology Language Guide. Edited by Michael K. Smith (Electronic Data Systems), Chris Welty (IBM Research), and Deborah McGuinness (Stanford University). W3C Working Draft 31-March-2003. This version URL: http://www.w3.org/TR/2003/WD-owl-guide-20030331/. Latest version URL: http://www.w3.org/TR/owl-guide/. "The OWL Web Ontology Language is intended to provide a language that can be used to describe the classes and relations between them that are inherent in Web documents and applications. This document demonstrates the use of the OWL language to: (1) formalize a domain by defining classes and properties of those classes, (2) define individuals and assert properties about them, and (3) reason about these classes and individuals to the degree permitted by the formal semantics of the OWL language. The sections are organized to present an incremental definition of a set of classes, properties and individuals, beginning with the fundamentals and proceeding to more complex language components..."

4. OWL Web Ontology Language Semantics and Abstract Syntax. Edited by Peter F. Patel-Schneider (Bell Labs Research, Lucent Technologies), Patrick Hayes (IHMC, University of West Florida), and Ian Horrocks (Department of Computer Science, University of Manchester). W3C Working Draft 31-March-2003. Version URL: http://www.w3.org/TR/2003/WD-owl-semantics-20030331/. Latest version URL: http://www.w3.org/TR/owl-semantics/. "This description of OWL, the Web Ontology Language being designed by the W3C Web Ontology Working Group, contains a high-level abstract syntax for both OWL DL and OWL Lite, sublanguages of OWL. A model-theoretic semantics is given to provide a formal meaning for OWL ontologies written in this abstract syntax. A model-theoretic semantics in the form of an extension to the RDF semantics is also given to provide a formal meaning for OWL ontologies as RDF graphs (OWL Full). A mapping from the abstract syntax to RDF graphs is given and the two model theories are shown to have the same consequences on OWL ontologies that can be written in the abstract syntax..."

5. Web Ontology Language (OWL) Use Cases and Requirements. Edited by Jeff Heflin (Lehigh University). W3C Working Draft 31-March-2003. Version URL: http://www.w3.org/TR/2003/WD-webont-req-20030331/. Latest version URL: http://www.w3.org/TR/webont-req/. "The Semantic Web is a vision for the future of the Web in which information is given explicit meaning, making it easier for machines to automatically process and integrate information available on the Web. The Semantic Web will build on XML's ability to define customized tagging schemes and RDF's flexible approach to representing data. The next element required for the Semantic Web is a Web ontology language which can formally describe the semantics of classes and properties used in web documents. In order for machines to perform useful reasoning tasks on these documents, the language must go beyond the basic semantics of RDF Schema. This document will enumerate the current requirements of such a language. It is expected that future languages will extend this one, adding, among other things, greater logical capabilities and the ability to establish trust on the Semantic Web. This document motivates the need for a Web ontology language by describing six use cases. Some of these use cases are based on efforts currently underway in industry and academia, others demonstrate more long-term possibilities. The use cases are followed by design goals that describe high-level objectives and guidelines for the development of the language. These design goals will be considered when evaluating proposed features. The section on Requirements presents a set of features that should be in the language and gives motivations for those features. The Objectives section describes a list of features that might be useful for many use cases but may not necessarily be addressed by the working group..."

6. OWL Web Ontology Language Test Cases. Edited by Jeremy J. Carroll (HP) and Jos De Roo (AGFA). W3C Working Draft 31-March-2003. Version URL: http://www.w3.org/TR/2003/WD-owl-test-20030331/. Latest version URL: http://www.w3.org/TR/owl-test/. "This document contains and presents test cases for the Web Ontology Language (OWL) approved by the Web Ontology Working Group. Many of the test cases illustrate the correct usage of the Web Ontology Language (OWL), and the formal meaning of its constructs. Other test cases illustrate the resolution of issues considered by the working group. Conformance for OWL documents and OWL document checkers is specified... We particular seek reports from implementators concerning both errors in the tests and successful execution of these tests, both proposed and approved. The tests are still in development. Each test may be edited or have a change of status according to the process specified below. Further tests are being added. Reviewers should note in particular that the syntactic levels indicated with each test file (Lite, DL, Full) have never been validated, and have not been updated in light of recent working group decisions. An editors' version of this document, with the latest tests, can be found at online. Other expected changes are indicated by editors' notes, and in Appendix D. Despite this flux, the working group would value implementor feedback on the tests both in this document and those found in the editors' version. Contributions of additional tests are invited.