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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.
This is a Last Call Working Draft. The first release of this document was 29 July 2002 and the Web Ontology Working Group has made its best effort to address comments recieved since then, releasing several drafts and resolving a list of issues meanwhile. The working group seeks confirmation that comments have been addressed to the satisfaction of the community.
This document depends normatively on [RDF MT] and anticipates some changes in that document based on comments from reviewers. Depending on the disposition of the requested changes to [RDF MT], some conflicts with details of this specification (such as section section 5.2 OWL Interpretations) may need to be resolved in subsequent drafts of this document. While the resolution may involve changes to the design that are observable in test cases, the changes are expected to be obscure enough that the impact to most readers and implementors will be negligible.
Comments on this document are due 9 May 2003. They should be sent to email@example.com, a mailing list with a public archive. General discussion of related technology is welcome in www-rdf-logic.
This document has been produced as part of the W3C Semantic Web Activity (Activity Statement). A list of patent disclosures related to this work is maintained by W3C, regardless of whether any such disclosures have been made or not.
This is a W3C Working Draft for review by W3C members and other interested parties. It is a draft document and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use W3C Working Drafts as reference materials or to cite them as other than "work in progress." A list of current W3C Recommendations and other technical documents can be found at http://www.w3.org/TR/.
This document contains several interrelated specifications of the several styles of OWL, the Web Ontology Language being produced by the W3C Web Ontology Working Group (WebOnt). First, Section 2 contains a high-level, abstract syntax for both OWL Lite, a subset of OWL, and OWL DL, a fuller style of using OWL but one that still places some limitations on how OWL ontologies are constructed. Eliminating these limitations results in the full OWL language, called OWL Full, which has the same syntax as RDF. The normative exchange syntax for OWL is RDF/XML [RDF Syntax]; the OWL Reference document [OWL Reference] shows how the RDF syntax is used in OWL. A mapping from the OWL abstract syntax to RDF graphs [RDF Concepts] is, however, provided in Section 4.
This document contains two formal semantics for OWL. One of these semantics, defined in Section 3, is a direct, standard model-theoretic semantics for OWL ontologies written in the abstract syntax. The other, defined in Section 5, is a vocabulary extension of the RDF semantics [RDF MT] that provides semantics for OWL ontologies in the form of RDF graphs. Two versions of this second semantics are provided, one that corresponds more closely to the direct semantics (and is thus a semantics for OWL DL) and one that can be used in cases where classes need to be treated as individuals or other situations that cannot be handled in the abstract syntax (and is thus a semantics for OWL Full). These two versions are actually very close, only differing in how they divide up the domain of discourse.
Appendix A contains a proof that the direct and RDFS-compatible semantics have the same consequences on OWL ontologies that correspond to abstract OWL ontologies that separate OWL individuals, OWL classes, OWL properties, and the RDF, RDFS, and OWL structural vocabulary. For such OWL ontologies the direct model theory is authoritative and the RDFS-compatible model theory is secondary. Appendix A also contains the sketch of a proof that the entailments in the RDFS-compatible semantics for OWL Full include all the entailments in the RDFS-compatible semantics for OWL DL. Finally a few examples of the various concepts defined in the document are presented in Appendix B.
This document is designed to be read by those interested in the technical details of OWL. It is not particularly intended for the casual reader, who should probably first read the OWL Guide [OWL Guide]. Developers of parsers and other syntactic tools for OWL will be particularly interested in Sections 2 and 4. Developers of reasoners and other semantic tools for OWL will be particulary interested in Sections 3 and 5.
The following table provides pointers to information about each element of the OWL vocabulary, as well as some elements of the RDF and RDFS vocabularies. The first column points to the vocabulary element's major definition in the abstract syntax of Section 2. The second column points to the vocabulary element's major definition in the OWL Lite abstract syntax. The third column points to the vocabularly element's major definition in the direct semantics of Section 3. The fourth column points to the major piece of the translation from the abstract syntax to triples for the vocabulary element Section 4. The fifth column points to the vocabularly element's major definition in the RDFS-compatible semantics of Section 5.
|Vocabulary Term||Abstract OWL DL Syntax||Abstract OWL Lite Syntax||Direct Semantics||Mapping to Triples||RDFS-Compatible Semantics|
The Joint US/EU ad hoc Agent Markup Language Committee developed DAML+OIL, which is the direct precursor to OWL. Many of the ideas in DAM+OIL and thus in OWL are also present in the Ontology Inference Layer (OIL). Many of the other members of the W3C Web Ontology Working Group have had substantial input into this document.
This document is the result of extensive discussions within the Web Ontology Working Group as a whole. The members of this group working group included: Yasser al Safadi, Jean-François Baget, James Barnette, Sean Bechhofer, Jonathan Borden, Frederik Brysse, Stephen Buswell, Peter Crowther, Jos De Roo, David De Roure, Mike Dean, Larry Eshelman, Jérôme, Dieter Fensel, Tim Finin, Nicholas Gibbins, Pat Hayes, Jeff Heflin, Ziv Hellman, James Hendler, Bernard Horan, Masahiro Hori, Ian Horrocks, Francesco Iannuzzelli, Mario Jeckle, Ruediger Klein, Ora Lassila, Alexander Maedche, Massimo Marchiori, Deborah McGuinness, Libby Miller, Enrico Motta, Leo Obrst, Laurent Olivry , Peter Patel-Schneider, Martin Pike, Marwan Sabbouh, Guus Schreiber, Shimizu Noboru, Michael Sintek, Michael Smith, Ned Smith, John Stanton, Lynn Andrea Stein, Herman ter Horst, Lynne R. Thompson, David Trastour, Frank van Harmelen, Raphael Volz, Evan Wallace, Christopher Welty, and John Yanosy.