W3C

OWL 2 Web Ontology Language
Quick Reference Guide

W3C Recommendation 27 October 2009

This version:
http://www.w3.org/TR/2009/REC-owl2-quick-reference-20091027/
Latest version (series 2):
http://www.w3.org/TR/owl2-quick-reference/
Latest Recommendation:
http://www.w3.org/TR/owl-quick-reference
Previous version:
http://www.w3.org/TR/2009/PR-owl2-quick-reference-20090922/ (color-coded diff)
Editors:
Jie Bao, Rensselaer Polytechnic Institute
Elisa F. Kendall, Sandpiper Software, Inc.
Deborah L. McGuinness, Rensselaer Polytechnic Institute
Peter F. Patel-Schneider, Bell Labs Research, Alcatel-Lucent
Contributors:
Li Ding, Rensselaer Polytechnic Institute
Ankesh Khandelwal, Rensselaer Polytechnic Institute

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

This document is also available in these non-normative formats: PDF version, Reference Card.

See also translations.

Copyright © 2009 W3C® (MIT, ERCIM, Keio), All Rights Reserved. W3C liability, trademark and document use rules apply.

Abstract

The OWL 2 Web Ontology Language, informally OWL 2, is an ontology language for the Semantic Web with formally defined meaning. OWL 2 ontologies provide classes, properties, individuals, and data values and are stored as Semantic Web documents. OWL 2 ontologies can be used along with information written in RDF, and OWL 2 ontologies themselves are primarily exchanged as RDF documents. The OWL 2 Document Overview describes the overall state of OWL 2, and should be read before other OWL 2 documents.

This document provides a non-normative quick reference guide to the OWL 2 language. It also provides links to other documents, including the OWL 2 Primer for language introduction and examples, the OWL 2 Structural Specification and Functional Syntax document for more details of the functional syntax, and the OWL 2 New Features and Rationale document for new feature descriptions.

Status of this Document

May Be Superseded

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/.

XML Schema Datatypes Dependency

OWL 2 is defined to use datatypes defined in the XML Schema Definition Language (XSD). As of this writing, the latest W3C Recommendation for XSD is version 1.0, with version 1.1 progressing toward Recommendation. OWL 2 has been designed to take advantage of the new datatypes and clearer explanations available in XSD 1.1, but for now those advantages are being partially put on hold. Specifically, until XSD 1.1 becomes a W3C Recommendation, the elements of OWL 2 which are based on it should be considered optional, as detailed in Conformance, section 2.3. Upon the publication of XSD 1.1 as a W3C Recommendation, those elements cease to be optional and are to be considered required as otherwise specified.

We suggest that for now developers and users follow the XSD 1.1 Candidate Recommendation. Based on discussions between the Schema and OWL Working Groups, we do not expect any implementation changes will be necessary as XSD 1.1 advances to Recommendation.

Summary of Changes

There have been no substantive changes since the previous version. For details on the minor changes see the change log and color-coded diff.

Please Send Comments

Please send any comments to public-owl-comments@w3.org (public archive). Although work on this document by the OWL Working Group is complete, comments may be addressed in the errata or in future revisions. Open discussion among developers is welcome at public-owl-dev@w3.org (public archive).

Endorsed By W3C

This document has been reviewed by W3C Members, by software developers, and by other W3C groups and interested parties, and is endorsed by the Director as a W3C Recommendation. It is a stable document and may be used as reference material or cited from another document. 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.

Patents

This document was produced by a group operating under the 5 February 2004 W3C Patent Policy. This document is informative only. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent.

Table of Contents


1 Names, Prefixes, and Notation

Names in OWL 2 are IRIs, often written in a shorthand prefix:localname, where prefix: is a prefix name that expands to an IRI, and localname is the remainder of the name. The standard prefix names in OWL 2 are:

Prefix Name Expansion
rdf:http://www.w3.org/1999/02/22-rdf-syntax-ns#
rdfs:http://www.w3.org/2000/01/rdf-schema#
owl:http://www.w3.org/2002/07/owl#
xsd:http://www.w3.org/2001/XMLSchema#

We use notation conventions in the following tables*:

Letters Meaning Letters Meaning Letters Meaning Letters Meaning
C class expression CN class name D data range DN datatype name
P object property expression PN object property name R data property A annotation property
a individual aN individual name _:a anonymous individual (a blank node label) v literal
n non-negative integer** f facet ON ontology name U IRI
s IRI or anonymous individual t IRI, anonymous individual, or literal p prefix name _:x blank node
(a1 … an) RDF list

* All of the above can have subscripts. ** as a shorthand for "n"^^xsd:nonNegativeInteger

2 OWL 2 constructs and axioms

For an OWL 2 DL ontology, there are some global restrictions on axioms.

In the following tables the first column provides links to the Primer (if applicable), the second column provides links to the Functional Syntax, and the third column gives RDF triples in the Turtle syntax.

2.1 Class Expressions

Predefined and Named Classes

Language FeatureFunctional SyntaxRDF Syntax
named class CN CN
universal class owl:Thing owl:Thing
empty class owl:Nothing owl:Nothing

Boolean Connectives and Enumeration of Individuals

Language FeatureFunctional SyntaxRDF Syntax
intersection ObjectIntersectionOf(C1 … Cn) _:x rdf:type owl:Class.
_:x owl:intersectionOf ( C1 … Cn ).
union ObjectUnionOf(C1 … Cn) _:x rdf:type owl:Class.
_:x owl:unionOf ( C1 … Cn ).
complement ObjectComplementOf(C) _:x rdf:type owl:Class.
_:x owl:complementOf C.
enumeration ObjectOneOf(a1 … an) _:x rdf:type owl:Class.
_:x owl:oneOf ( a1 … an ).

Object Property Restrictions

Language FeatureFunctional SyntaxRDF Syntax
universal ObjectAllValuesFrom(P C) _:x rdf:type owl:Restriction.
_:x owl:onProperty P.
_:x owl:allValuesFrom C
existential ObjectSomeValuesFrom(P C) _:x rdf:type owl:Restriction.
_:x owl:onProperty P.
_:x owl:someValuesFrom C
individual value ObjectHasValue(P a) _:x rdf:type owl:Restriction.
_:x owl:onProperty P.
_:x owl:hasValue a.
local reflexivity ObjectHasSelf(P) _:x rdf:type owl:Restriction.
_:x owl:onProperty P.
_:x owl:hasSelf "true"^^xsd:boolean.
exact cardinality ObjectExactCardinality(n P) _:x rdf:type owl:Restriction.
_:x owl:onProperty P.
_:x owl:cardinality n.
qualified exact cardinality ObjectExactCardinality(n P C) _:x rdf:type owl:Restriction.
_:x owl:onProperty P.
_:x owl:qualifiedCardinality n.
_:x owl:onClass C.
maximum cardinality ObjectMaxCardinality(n P) _:x rdf:type owl:Restriction.
_:x owl:onProperty P.
_:x owl:maxCardinality n.
qualified maximum cardinality ObjectMaxCardinality(n P C) _:x rdf:type owl:Restriction.
_:x owl:onProperty P.
_:x owl:maxQualifiedCardinality n.
_:x owl:onClass C.
minimum cardinality ObjectMinCardinality(n P) _:x rdf:type owl:Restriction.
_:x owl:onProperty P.
_:x owl:minCardinality n.
qualified minimum cardinality ObjectMinCardinality(n P C) _:x rdf:type owl:Restriction.
_:x owl:onProperty P.
_:x owl:minQualifiedCardinality n.
_:x owl:onClass C.

Data Property Restrictions

Language FeatureFunctional SyntaxRDF Syntax
universal DataAllValuesFrom(R D) _:x rdf:type owl:Restriction.
_:x owl:onProperty R.
_:x owl:allValuesFrom D.
existential DataSomeValuesFrom(R D) _:x rdf:type owl:Restriction.
_:x owl:onProperty R.
_:x owl:someValuesFrom D.
literal value DataHasValue(R v) _:x rdf:type owl:Restriction.
_:x owl:onProperty R.
_:x owl:hasValue v.
exact cardinality DataExactCardinality(n R) _:x rdf:type owl:Restriction.
_:x owl:onProperty R.
_:x owl:cardinality n.
qualified exact cardinality DataExactCardinality(n R D) _:x rdf:type owl:Restriction.
_:x owl:onProperty R.
_:x owl:qualifiedCardinality n.
_:x owl:onDataRange D.
maximum cardinality DataMaxCardinality(n R) _:x rdf:type owl:Restriction.
_:x owl:onProperty R.
_:x owl:maxCardinality n.
qualified maximum cardinality DataMaxCardinality(n R D) _:x rdf:type owl:Restriction.
_:x owl:onProperty R.
_:x owl:maxQualifiedCardinality n.
_:x owl:onDataRange D.
minimum cardinality DataMinCardinality(n R) _:x rdf:type owl:Restriction.
_:x owl:onProperty R.
_:x owl:minCardinality n.
qualified minimum cardinality DataMinCardinality(n R D) _:x rdf:type owl:Restriction.
_:x owl:onProperty R.
_:x owl:minQualifiedCardinality n.
_:x owl:onDataRange D.

Restrictions Using n-ary Data Range

In the following table 'Dn' is an n-ary data range.

Language FeatureFunctional SyntaxRDF Syntax
n-ary universal DataAllValuesFrom(R1 … Rn Dn) _:x rdf:type owl:Restriction.
_:x owl:onProperties ( R1 … Rn ).
_:x owl:allValuesFrom Dn.
n-ary existential DataSomeValuesFrom(R1 … Rn Dn) _:x rdf:type owl:Restriction.
_:x owl:onProperties ( R1 … Rn).
_:x owl:someValuesFrom Dn.

2.2 Properties

Object Property Expressions

Language FeatureFunctional SyntaxRDF Syntax
named object property PN PN
universal object property owl:topObjectProperty owl:topObjectProperty
empty object property owl:bottomObjectProperty owl:bottomObjectProperty
inverse property ObjectInverseOf(PN) _:x owl:inverseOf PN

Data Property Expressions

Language FeatureFunctional SyntaxRDF Syntax
named data property R R
universal data property owl:topDataProperty owl:topDataProperty
empty data property owl:bottomDataProperty owl:bottomDataProperty

2.3 Individuals & Literals

Language FeatureFunctional SyntaxRDF Syntax
named individual aN aN
anonymous individual _:a _:a
literal (datatype value) "abc"^^DN "abc"^^DN

2.4 Data Ranges

Data Range Expressions

Language FeatureFunctional SyntaxRDF Syntax
named datatype DN DN
data range complement DataComplementOf(D) _:x rdf:type rdfs:Datatype.
_:x owl:datatypeComplementOf D.
data range intersection DataIntersectionOf(D1…Dn) _:x rdf:type rdfs:Datatype.
_:x owl:intersectionOf (D1…Dn).
data range union DataUnionOf(D1…Dn) _:x rdf:type rdfs:Datatype.
_:x owl:unionOf (D1…Dn).
literal enumeration DataOneOf(v1 … vn) _:x rdf:type rdfs:Datatype.
_:x owl:oneOf ( v1 … vn ).
datatype restriction DatatypeRestriction(DN f1 v1 … fn vn) _:x rdf:type rdfs:Datatype.
_:x owl:onDatatype DN.
_:x owl:withRestrictions (_:x1 ... _:xn).
_:xj fj vj.      j=1…n

2.5 Axioms

Class Expression Axioms

Language FeatureFunctional SyntaxRDF Syntax
subclass SubClassOf(C1 C2) C1 rdfs:subClassOf C2.
equivalent classes EquivalentClasses(C1 … Cn) Cj owl:equivalentClass Cj+1. j=1…n-1
disjoint classes DisjointClasses(C1 C2) C1 owl:disjointWith C2.
pairwise disjoint classes DisjointClasses(C1 … Cn) _:x rdf:type owl:AllDisjointClasses.
_:x owl:members ( C1 … Cn ).
disjoint union DisjointUnionOf(CN C1 … Cn) CN owl:disjointUnionOf ( C1 … Cn ).

Object Property Axioms

Language FeatureFunctional SyntaxRDF Syntax
subproperty SubObjectPropertyOf(P1 P2) P1 rdfs:subPropertyOf P2.
property chain inclusion SubObjectPropertyOf(ObjectPropertyChain(P1 … Pn) P) P owl:propertyChainAxiom (P1 … Pn).
property domain ObjectPropertyDomain(P C) P rdfs:domain C.
property range ObjectPropertyRange(P C) P rdfs:range C.
equivalent properties EquivalentObjectProperties(P1 … Pn) Pj owl:equivalentProperty Pj+1. j=1…n-1
disjoint properties DisjointObjectProperties(P1 P2) P1 owl:propertyDisjointWith P2.
pairwise disjoint properties DisjointObjectProperties(P1 … Pn) _:x rdf:type owl:AllDisjointProperties.
_:x owl:members ( P1 … Pn ).
inverse properties InverseObjectProperties(P1 P2) P1 owl:inverseOf P2.
functional property FunctionalObjectProperty(P) P rdf:type owl:FunctionalProperty.
inverse functional property InverseFunctionalObjectProperty(P) P rdf:type owl:InverseFunctionalProperty.
reflexive property ReflexiveObjectProperty(P) P rdf:type owl:ReflexiveProperty.
irreflexive property IrreflexiveObjectProperty(P) P rdf:type owl:IrreflexiveProperty.
symmetric property SymmetricObjectProperty(P) P rdf:type owl:SymmetricProperty.
asymmetric property AsymmetricObjectProperty(P) P rdf:type owl:AsymmetricProperty.
transitive property TransitiveObjectProperty(P) P rdf:type owl:TransitiveProperty.

Data Property Axioms

Language FeatureFunctional SyntaxRDF Syntax
subproperty SubDataPropertyOf(R1 R2) R1 rdfs:subPropertyOf R2.
property domain DataPropertyDomain(R C) R rdfs:domain C.
property range DataPropertyRange(R D) R rdfs:range D.
equivalent properties EquivalentDataProperties(R1 … Rn) Rj owl:equivalentProperty Rj+1. j=1…n-1
disjoint properties DisjointDataProperties(R1 R2) R1 owl:propertyDisjointWith R2.
pairwise disjoint properties DisjointDataProperties(R1 … Rn) _:x rdf:type owl:AllDisjointProperties.
_:x owl:members ( R1 … Rn ).
functional property FunctionalDataProperty(R) R rdf:type owl:FunctionalProperty.

Datatype Definitions

Language FeatureFunctional SyntaxRDF Syntax
datatype definition DatatypeDefinition(DN D) DN owl:equivalentClass D.

Assertions

Language FeatureFunctional SyntaxRDF Syntax
individual equality SameIndividual(a1 … an) aj owl:sameAs aj+1. j=1…n-1
individual inequality DifferentIndividuals(a1 a2) a1 owl:differentFrom a2.
pairwise individual inequality DifferentIndividuals(a1 … an) _:x rdf:type owl:AllDifferent.
_:x owl:members (a1 … an).
class assertion ClassAssertion(C a) a rdf:type C.
positive object property assertion ObjectPropertyAssertion( PN a1 a2 ) a1 PN a2.
positive data property assertion DataPropertyAssertion( R a v ) a R v.
negative object property assertion NegativeObjectPropertyAssertion(P a1 a2 ) _:x rdf:type owl:NegativePropertyAssertion.
_:x owl:sourceIndividual a1.
_:x owl:assertionProperty P.
_:x owl:targetIndividual a2.
negative data property assertion NegativeDataPropertyAssertion(R a v ) _:x rdf:type owl:NegativePropertyAssertion.
_:x owl:sourceIndividual a.
_:x owl:assertionProperty R.
_:x owl:targetValue v.

Keys

Language FeatureFunctional SyntaxRDF Syntax
Key HasKey(C (P1 … Pm) (R1 … Rn) ) C owl:hasKey (P1 … Pm R1 … Rn).
m+n>0


2.6 Declarations

Language FeatureFunctional SyntaxRDF Syntax
class Declaration( Class( CN ) ) CN rdf:type owl:Class.
datatype Declaration( Datatype( DN ) ) DN rdf:type rdfs:Datatype.
object property Declaration( ObjectProperty( PN ) ) PN rdf:type owl:ObjectProperty.
data property Declaration( DataProperty( R ) ) R rdf:type owl:DatatypeProperty.
annotation property Declaration( AnnotationProperty( A ) ) A rdf:type owl:AnnotationProperty.
named individual Declaration( NamedIndividual( aN ) ) aN rdf:type owl:NamedIndividual.

2.7 Annotations

Annotations

Language FeatureFunctional SyntaxRDF Syntax
annotation assertion AnnotationAssertion(A s t) s A t.
annotation of an axiom
where the axiom in RDF is one or more triples of the form si U ti, i.e., with the same predicate U. 		AXIOM(Annotation(A t) …) _:xi A t.
si U ti.
…
_:xi rdf:type owl:Axiom.
_:xi owl:annotatedSource si.
_:xi owl:annotatedProperty U.
_:xi owl:annotatedTarget ti.
annotation of an axiom
where the axiom in RDF is _:x U t1 		AXIOM(Annotation(A t) … )
 _:x A t.
_:x U t1.
…
annotation of another annotation
(the other annotation in RDF starts with s1) 		Annotation(Annotation(A t) … A1 t1) _:x A t.
s1 A1 t1.
…
_:x rdf:type owl:Annotation.
_:x owl:annotatedSource s1.
_:x owl:annotatedProperty A1.
_:x owl:annotatedTarget t1.

Annotation Properties

Language FeatureFunctional SyntaxRDF Syntax
named annotation property A A
human-readable name rdfs:label rdfs:label
human-readable comment rdfs:comment rdfs:comment
additional information rdfs:seeAlso rdfs:seeAlso
defining agent rdfs:isDefinedBy rdfs:isDefinedBy
version information owl:versionInfo owl:versionInfo
deprecation owl:deprecated owl:deprecated
backwards compatibility owl:backwardCompatibleWith owl:backwardCompatibleWith
incompatibility owl:incompatibleWith owl:incompatibleWith
prior version owl:priorVersion owl:priorVersion

Annotation Axioms

Language FeatureFunctional SyntaxRDF Syntax
annotation subproperties SubAnnotationPropertyOf(A1 A2) A1 rdfs:subPropertyOf A2.
annotation property domain AnnotationPropertyDomain(A U) A rdfs:domain U.
annotation property range AnnotationPropertyRange(A U) A rdfs:range U.

2.8 Ontologies

Ontologies

Language FeatureFunctional SyntaxRDF Syntax
OWL ontology
(importing)1 2
Ontology([ON [U]]
  Import(ON1)...
  Annotation(A t)
  ...
) 		ON rdf:type owl:Ontology.
[ON owl:versionIRI U.]
ON owl:imports ON1. ...
ON A t.
...
prefix declaration3 Prefix(p=U) @prefix p U.
  1. [ ] represents optional constructs
  2. In the RDF syntax _:x is used in place of ON if there is no ontology name.
  3. RDF syntax is in Turtle, other RDF serializations may vary.


3 Built-in Datatypes and Facets

3.1 Built-in Datatypes

Universal Datatype rdfs:Literal
Numbers owl:rational owl:real
xsd:double xsd:float xsd:decimal xsd:integer
xsd:long xsd:int xsd:short xsd:byte
xsd:nonNegativeInteger xsd:nonPositiveInteger
xsd:positiveInteger xsd:negativeInteger
xsd:unsignedLong xsd:unsignedInt
xsd:unsignedShort xsd:unsignedByte
Strings rdf:PlainLiteral (RDF plain literals)
xsd:string xsd:NCName xsd:Name xsd:NMTOKEN
xsd:token xsd:language xsd:normalizedString
Boolean Values xsd:boolean (value space: true and false)
Binary Data xsd:base64Binary xsd:hexBinary
IRIs xsd:anyURI
Time Instants xsd:dateTime (optional time zone offset)
xsd:dateTimeStamp (required time zone offset)
XML Literals rdf:XMLLiteral

3.2 Facets

Facet Value Applicable Datatypes Explanation
xsd:minInclusive
xsd:maxInclusive
xsd:minExclusive
xsd:maxExclusive 		literal in the corresponding datatype Numbers,
Time Instants 		Restricts the value-space to greater than (equal to) or lesser than (equal to) a value
xsd:minLength
xsd:maxLength
xsd:length 		Non-negative integer Strings,
Binary Data,
IRIs 		Restricts the value-space based on the
lengths of the literals
xsd:pattern xsd:string literal as a regular expression Strings,
IRIs 		Restricts the value space to literals that> match the regular expression
rdf:langRange xsd:string literal as a regular expression rdf:PlainLiteral Restricts the value space to literals with language tags that match the regular expression

4 Appendix

4.1 New Features in OWL 2

Class Expressions
Class Axioms
Property Expressions
Property Axioms
Data Ranges
Assertions
Annotation
Extra Built-in Datatypes
  • owl:rational, owl:real, xsd:dateTimeStamp, rdf:PlainLiteral
Others

4.2 Additional Vocabulary in OWL 2 RDF Syntax

Feature Vocabulary Note
data range owl:DataRange deprecated in OWL 2, replaced by rdfs:Datatype
membership of a set of pairwise different individuals owl:distinctMembers can alternatively use owl:members
ontology property owl:OntologyProperty
deprecation owl:DeprecatedClass,
owl:DeprecatedProperty 		alternative RDF syntax:
s rdf:type owl:DeprecatedClass . or
s rdf:type owl:DeprecatedProperty .
can be replaced by

s owl:deprecated "true"^^xsd:boolean .

5 Appendix: Change Log (Informative)

5.1 Changes Since Proposed Recommendation

This section summarizes the changes to this document since the Proposed Recommendation of 22 September, 2009.

5.2 Changes Since Last Call

This section summarizes the changes to this document since the Candidate Recommendation of 11 June, 2009.

6 Acknowledgments

The starting point for the development of OWL 2 was the OWL1.1 member submission, itself a result of user and developer feedback, and in particular of information gathered during the OWL Experiences and Directions (OWLED) Workshop series. The working group also considered postponed issues from the WebOnt Working Group.

This document has been produced by the OWL Working Group (see below), and its contents reflect extensive discussions within the Working Group as a whole. The editors extend special thanks to Bernardo Cuenca Grau (Oxford University), Christine Golbreich (Université de Versailles St-Quentin and LIRMM), Ivan Herman (W3C/ERCIM), and Bijan Parsia (University of Manchester) for their thorough reviews.

The regular attendees at meetings of the OWL Working Group at the time of publication of this document were: Jie Bao (RPI), Diego Calvanese (Free University of Bozen-Bolzano), Bernardo Cuenca Grau (Oxford University Computing Laboratory), Martin Dzbor (Open University), Achille Fokoue (IBM Corporation), Christine Golbreich (Université de Versailles St-Quentin and LIRMM), Sandro Hawke (W3C/MIT), Ivan Herman (W3C/ERCIM), Rinke Hoekstra (University of Amsterdam), Ian Horrocks (Oxford University Computing Laboratory), Elisa Kendall (Sandpiper Software), Markus Krötzsch (FZI), Carsten Lutz (Universität Bremen), Deborah L. McGuinness (RPI), Boris Motik (Oxford University Computing Laboratory), Jeff Pan (University of Aberdeen), Bijan Parsia (University of Manchester), Peter F. Patel-Schneider (Bell Labs Research, Alcatel-Lucent), Sebastian Rudolph (FZI), Alan Ruttenberg (Science Commons), Uli Sattler (University of Manchester), Michael Schneider (FZI), Mike Smith (Clark & Parsia), Evan Wallace (NIST), Zhe Wu (Oracle Corporation), and Antoine Zimmermann (DERI Galway). We would also like to thank past members of the working group: Jeremy Carroll, Jim Hendler, Vipul Kashyap.