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OWL Web Ontology Language
Semantics and Abstract Syntax

W3C Recommendation 10 February 2004

New Version Available: OWL 2 (Document Status Update, 12 November 2009)

The OWL Working Group has produced a W3C Recommendation for a new version of OWL which adds features to this 2004 version, while remaining compatible. Please see OWL 2 Document Overview for an introduction to OWL 2 and a guide to the OWL 2 document set.

This version:
http://www.w3.org/TR/2004/REC-owl-semantics-20040210/
Latest version:
http://www.w3.org/TR/owl-semantics/
Previous version:
http://www.w3.org/TR/2003/PR-owl-semantics-20031215/
Editors:
Peter F. Patel-Schneider, Bell Labs Research, Lucent Technologies
Patrick Hayes, IHMC, University of West Florida
Ian Horrocks, Department of Computer Science, University of Manchester

Please refer to the errata for this document, which may include some normative corrections.

This document is also available in this non-normative form: single HTML file.

See also translations.

Copyright © 2004 W3C® (MIT, ERCIM, Keio), All Rights Reserved. W3C liability, trademark, document use and software licensing rules apply.

Abstract

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.

Status of this document

This document has been reviewed by W3C Members and other interested parties, and it has been endorsed by the Director as a W3C Recommendation. W3C's role in making the Recommendation is to draw attention to the specification and to promote its widespread deployment. This enhances the functionality and interoperability of the Web.

This is one of six parts of the W3C Recommendation for OWL, the Web Ontology Language. It has been developed by the Web Ontology Working Group as part of the W3C Semantic Web Activity (Activity Statement, Group Charter) for publication on 10 February 2004.

The design of OWL expressed in earlier versions of these documents has been widely reviewed and satisfies the Working Group's technical requirements. The Working Group has addressed all comments received, making changes as necessary. Changes to this document since the Proposed Recommendation version are detailed in the change log.

Comments are welcome at public-webont-comments@w3.org (archive) and general discussion of related technology is welcome at www-rdf-logic@w3.org (archive).

A list of implementations is available.

The W3C maintains a list of any patent disclosures related to this work.

This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at http://www.w3.org/TR/.

Table of contents

1. Introduction (Informative)

This document is one part of the specification of OWL, the Web Ontology Language. The OWL Overview [OWL Overview] describes each of the different documents in the specification and how they fit together.

This document contains several interrelated normative 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 Semantics] 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. 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 particularly interested in Sections 3 and 5.

Appendix C. Changes from Last Call (Informative)

This appendix provides an informative account of the changes from the last-call version of this document. All substantive post-last call changes to the document, as well as some editorial post-last-call changes, are indicated in the style of this appendix.

C.1 Substantive changes after Last Call

This section provides information on the post Last Call changes to the document that make changes to the specification of OWL.

C.2 Editorial changes after Last Call

This section provides information on post Last Call editorial changes to the document, i.e., changes that do not affect the specification of OWL.

C.3 Substantive changes after Candidate Recommendation

This section provides information on the post Candidate Recommendation changes to the document that make changes to the specification of OWL.

C.4 Editorial changes after Candidate Recommendation

This section provides information on post Candidate Recommendation editorial changes to the document, i.e., changes that do not affect the specification of OWL.

C.5 Changes since Proposed Recommendation

This section provides information on post Proposed Recommendation changes to the document.

Index of Vocabulary (Informative)

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 Terms
Vocabulary Term Abstract OWL DL Syntax Abstract OWL Lite Syntax Direct Semantics Mapping to Triples RDFS-Compatible Semantics
owl:AllDifferent 4.1 5.2
owl:allValuesFrom 2.3.2.3 2.3.1.2 3.2 4.1 5.2
owl:AnnotationProperty 2.3.1.3 2.3.2.4 3.2 4.1 5.2
owl:backwardCompatibleWith 2.1 2.1 4.1
owl:cardinality 2.3.2.3 2.3.1.2 3.2 4.1 5.2
owl:Class 2.3.2.1 2.3.1.1 3.3 4.1 5.2
owl:complementOf 2.3.2.2 3.2 4.1 5.2
owl:DatatypeProperty 2.3.2.4 2.3.1.3 3.3 4.1 5.2
owl:DeprecatedClass 2.3.2.1 2.3.1.1 3.3 4.1 5.2
owl:DeprecatedProperty 2.3.2.4 2.3.1.3 3.3 4.1 5.2
owl:DataRange 2.3.2.3 2.3.1.2 3.2 4.1 5.2
owl:differentFrom 2.2 2.2 3.3 4.1 5.2
owl:disjointWith 2.3.2.1 3.3 4.1 5.2
owl:distinctMembers 4.1 5.2
owl:equivalentClass 2.3.2.1 2.3.1.1 3.3 4.1 5.2
owl:equivalentProperty 2.3.1.3 2.3.1.3 3.3 4.1 5.2
owl:FunctionalProperty 2.3.2.4 2.3.1.3 3.3 4.1 5.2
owl:hasValue 2.3.2.3 3.2 4.1 5.2
owl:imports 2.1 2.1 3.4 4.1 5.4
owl:incompatibleWith 2.1 2.1 4.1
owl:intersectionOf 2.3.2.2 3.2 4.1 5.2
owl:InverseFunctionalProperty 2.3.2.4 2.3.1.3 3.3 4.1 5.2
owl:inverseOf 2.3.2.4 2.3.1.3 3.3 4.1 5.2
owl:maxCardinality 2.3.2.3 2.3.1.2 3.2 4.1 5.2
owl:minCardinality 2.3.2.3 2.3.1.2 3.2 4.1 5.2
owl:Nothing 2.1 2.1 3.2 4.1 5.2
owl:ObjectProperty 2.3.2.4 2.3.1.3 3.3 4.1 5.2
owl:oneOf 2.3.2.2 3.2 4.1 5.2
owl:onProperty 2.3.2.3 2.3.1.2 3.2 4.1 5.2
owl:Ontology 2.1 2.1 3.4 4.1 5.2
owl:OntologyProperty 2.3.1.3 2.3.2.4 3.2 4.1 5.2
owl:priorVersion 2.1 2.1 4.1
owl:Restriction 2.3.2.3 2.3.1.2 3.2 4.1 5.2
owl:sameAs 2.2 2.2 3.3 4.1 5.2
owl:someValuesFrom 2.3.2.3 2.3.1.2 3.2 4.1 5.2
owl:SymmetricProperty 2.3.2.4 2.3.1.3 3.3 4.1 4.2
owl:Thing 2.1 2.1 3.2 4.1 5.2
owl:TransitiveProperty 2.3.2.4 2.3.1.3 3.3 4.1 5.2
owl:unionOf 2.3.2.2 3.2 4.1 5.2
owl:versionInfo 2.1 2.1 4.1
rdf:List 4.1 5.2
rdf:nil 4.1 5.2
rdf:type 2.2 2.2 3.3 4.1
rdfs:comment 2.1 2.1 4.1
rdfs:Datatype 4.1 5.2
rdfs:domain 2.3.2.4 2.3.1.3 3.3 4.1 5.2
rdfs:label 2.1 2.1 4.1
rdfs:Literal 2.3.1.3 2.3.2.3 4.1 4.1 5.2
rdfs:range 2.3.2.4 2.3.1.3 3.3 4.1 5.2
rdfs:subClassOf 2.3.2.1 2.3.1.1 3.3 4.1 5.2
rdfs:subPropertyOf 2.3.1.3 2.3.1.3 3.3 4.1 5.2

Acknowledgments

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 DAML+OIL and thus in OWL are also present in the Ontology Inference Layer (OIL).

This document is the result of extensive discussions within the Web Ontology Working Group as a whole. The participants in this working group included: Yasser alSafadi, Jean-François Baget, James Barnette, Sean Bechhofer, Jonathan Borden, Frederik Brysse, Stephen Buswell, Jeremy Carroll, Dan Connolly, Peter Crowther, Jonathan Dale, Jos De Roo, David De Roure, Mike Dean, Larry Eshelman, Jérôme Euzenat, Tim Finin, Nicholas Gibbins, Sandro Hawke, Patrick Hayes, Jeff Heflin, Ziv Hellman, James Hendler, Bernard Horan, Masahiro Hori, Ian Horrocks, Jane Hunter, Francesco Iannuzzelli, Rüdiger Klein, Natasha Kravtsova, Ora Lassila, Massimo Marchiori, Deborah McGuinness, Enrico Motta, Leo Obrst, Mehrdad Omidvari, Martin Pike, Marwan Sabbouh, Guus Schreiber, Noboru Shimizu, Michael Sintek, Michael K. Smith, John Stanton, Lynn Andrea Stein, Herman ter Horst, David Trastour, Frank van Harmelen, Bernard Vatant, Raphael Volz, Evan Wallace, Christopher Welty, Charles White, and John Yanosy.

References

Normative References

[RDF Concepts]
Resource Description Framework (RDF): Concepts and Abstract Syntax, Graham Klyne and Jeremy J. Carroll, Editors, W3C Recommendation, 10 February 2004, http://www.w3.org/TR/2004/REC-rdf-concepts-20040210/ . Latest version available at http://www.w3.org/TR/rdf-concepts/ .
[RDF Semantics]
RDF Semantics, Patrick Hayes, Editor, W3C Recommendation, 10 February 2004, http://www.w3.org/TR/2004/REC-rdf-mt-20040210/ . Latest version available at http://www.w3.org/TR/rdf-mt/ .
[RDF Syntax]
RDF/XML Syntax Specification (Revised), Dave Beckett, Editor, W3C Recommendation, 10 February 2004, http://www.w3.org/TR/2004/REC-rdf-syntax-grammar-20040210/ . Latest version available at http://www.w3.org/TR/rdf-syntax-grammar/ .
[RDF Tests]
RDF Test Cases, Jan Grant and Dave Beckett, Editors, W3C Recommendation, 10 February 2004, http://www.w3.org/TR/2004/REC-rdf-testcases-20040210/ . Latest version available at http://www.w3.org/TR/rdf-testcases/ .
[XML]
Extensible Markup Language (XML) 1.0 (Second Edition). Tim Bray, Jean Paoli, C. M. Sperberg-McQueen, and Eve Maler, eds. W3C Recommendation 6 October 2000. Latest version is available at http://www.w3.org/TR/REC-xml.
[XML Schema Datatypes]
XML Schema Part 2: Datatypes.. Paul V. Biron and Ashok Malhotra, eds. W3C Recommendation 02 May 2001. Latest version is available at http://www.w3.org/TR/xmlschema-2/.

Other References

[DAML+OIL]
DAML+OIL (March 2001) Reference Description. Dan Connolly, Frank van Harmelen, Ian Horrocks, Deborah L. McGuinness, Peter F. Patel-Schneider, and Lynn Andrea Stein. W3C Note 18 December 2001. Latest version is available at http://www.w3.org/TR/daml+oil-reference.
[OWL Guide]
OWL Web Ontology Language Guide, Michael K. Smith, Chris Welty, and Deborah L. McGuinness, Editors, W3C Recommendation, 10 February 2004, http://www.w3.org/TR/2004/REC-owl-guide-20040210/ . Latest version available at http://www.w3.org/TR/owl-guide/ .
[OWL Issues]
Web Ontology Issue Status. Michael K. Smith, ed. 27 June 2003.
[OWL Overview]
OWL Web Ontology Language Overview, Deborah L. McGuinness and Frank van Harmelen, Editors, W3C Recommendation, 10 February 2004, http://www.w3.org/TR/2004/REC-owl-features-20040210/ . Latest version available at http://www.w3.org/TR/owl-features/ .
[OWL Reference]
OWL Web Ontology Language Reference, Mike Dean and Guus Schreiber, Editors, W3C Recommendation, 10 February 2004, http://www.w3.org/TR/2004/REC-owl-ref-20040210/ . Latest version available at http://www.w3.org/TR/owl-ref/ .
[RDF Syntax]
RDF/XML Syntax Specification (Revised), Dave Beckett, Editor, W3C Recommendation, 10 February 2004, http://www.w3.org/TR/2004/REC-rdf-syntax-grammar-20040210/ . Latest version available at http://www.w3.org/TR/rdf-syntax-grammar/ .
[RDF Vocabulary]
RDF Vocabulary Description Language 1.0: RDF Schema, Dan Brickley and R. V. Guha, Editors, W3C Recommendation, 10 February 2004, http://www.w3.org/TR/2004/REC-rdf-schema-20040210/ . Latest version available at http://www.w3.org/TR/rdf-schema/ .