OWL Web Ontology Language Semantics and Abstract Syntax
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 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 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/.
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.
[10 April 2003]
In response to
http://lists.w3.org/Archives/Public/www-webont-wg/2003Apr/0046.html,
added owl:Class,
owl:Restriction,
owl:ObjectProperty,
owl:DatatypeProperty,
owl:AnnotationProperty,
owl:OntologyProperty,
owl:Ontology,
owl:AllDifferent,
owl:FunctionalProperty,
owl:InverseFunctionalProperty,
owl:SymmetricProperty, and
owl:TransitiveProperty
to CI
in Section 5.2. Some of these were
inferrable already.
[30 May 2003]
Per a decision of the Web Ontology working group on 29 May 2003 to
add axioms for ontology properties,
recorded in
http://lists.w3.org/Archives/Public/www-webont-wg/2003May/0402.html,
added axioms for ontology properties to the OWL Lite and OWL DL
abstract syntax in Sections 2.3.1.3.
and Section 2.3.2.4;
added direct semantics conditions for ontology property axioms
in Section 3.3; and
added a mapping for ontology property axioms
in Section 4.1.
Fixed the proofs of Lemma 2
and Lemma 3.
[30 May 2003]
Per a decision of the Web Ontology working group on 29 May 2003 to
change the semantics for
owl:intersectionOf and related
resources from an intensional semantics to an extensional semantics,
recorded in
http://lists.w3.org/Archives/Public/www-webont-wg/2003May/0402.html,
modified the semantic conditions for
owl:intersectionOf,
owl:unionOf,
owl:complementOf, and
owl:oneOf
in Section 5.2.
No change needed to be made to the proof of
Lemma 1.
Fixed the proofs of
Lemma 4 and
Lemma 2.
[6 June 2003]
Changed the treatment of datatypes to correspond with the
substantive post-last-call fixes and changes to the treatment of
datatypes in RDF.
Changes have been made in
Section 3.1 and
Appendix A.1.
[30 June 2003]
Fixed a bug in the semantic conditions for
owl:hasValue
noticed by Jeremy Carroll, changing the conditions for the value
from a property to an individual or a data value
in Section 5.2.
[23 July 2003]
In response to a substantive post-last-call change to the RDF semantics,
changing the if-and-only-if conditions for
rdfs:subClassOf and
rdfs:subPropertyOf to only-if
conditions,
added if-and-only-if conditions for
rdfs:subClassOf,
over OWL classes, and
rdfs:subPropertyOf,
over OWL individual-valued properties and
over OWL datatype properties,
to Section 5.2.
[23 July 2003]
In response to a substantive change to the RDF syntax mapping to
triples, removing the typing triples for collections,
[applicable document unknown],
made typing of list resources optional in
Section 4.1.
Also modified an example in
Appendix B.1.
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.
[14 April 2003]
In response to
http://lists.w3.org/Archives/Public/public-webont-comments/2003Apr/0029.html,
point 1, added
``Because there is no standard way to go from a URI reference to an XML
Schema datatype in an XML Schema, there is no standard way to use
user-defined XML Schema datatypes in OWL.''
to the discussion of allowable XML Schema datatypes in
Section 2.
[3 October 2003]
In response to
http://lists.w3.org/Archives/Public/www-webont-wg/2003Sep/0177.html,
augmented the mapping from the abstract syntax to triples to allow
for collections of axioms and facts outside of ontologies to
generate OWL DL in triples
made the type triple for anonymous ontologies optional unless the
ontology has annotations. Upgraded the definition of entailment
in the direct model theory to allow entailment to work over
collections of axioms and facts outside of ontologies.
Changes were made in
Section 3.4,
Section 4.2, and
Section 5.4.
Many of the proofs in Appendix A
required minor changes.
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.
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.
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.
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/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
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/ .
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 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 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/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/ .