N.B. This document refers to the SKOS Core Vocabulary, which has been modified since the publication of this document series. Please see http://www.w3.org/2004/02/skos/core/guide/ for the latest version of the SKOS Core Guide.

Abstract:
This report describes the features of OWL that are used in the SKOS-Core 1.0 schema for thesaurus data to express additional semantics and constraints that may not be expressed with RDF schema alone.
Project name:
Semantic Web Advanced Development for Europe (SWAD-Europe)
Project Number:
IST-2001-34732
Workpackage name:
8. Thesaurus Research Prototype
Workpackage description:
http://www.w3.org/2001/sw/Europe/plan/workpackages/live/esw-wp-8.html 
Deliverable title:
8.6: thesaurus_daml_oil_report
This version:
http://www.w3.org/2001/sw/Europe/reports/thes/8.6/draft01.html
Latest version:
http://www.w3.org/2001/sw/Europe/reports/thes/8.6/
Authors:
Alistair J. Miles, CCLRC

Status of this document

This section describes the status of this document at the time of its publication. This is a draft document and may be updated, replaced, or obsoleted by other documents at any time. The latest status of this document series is maintained at the W3C.

This document is a public DRAFT for discussion. This guide and the SKOS-Core schema are an output of the research work of the Semantic Web Advanced Development for Europe Project, which is associated with the W3C Semantic Web Activity. This document is made available by W3C for discussion only. Publication of this document by W3C does not imply endorsement by W3C, including the Team and Membership.

Comments on this document are welcome and should be sent to the authors or to the public-esw-thes@w3.org list. An archive of this list is available at http://lists.w3.org/Archives/Public/public-esw-thes/.

Contents

References

Appendix: SKOS-Core 1.0 Schema

1. Introduction   [back to contents]

This report describes the features of OWL [OWL] that were used in the 1.0 release of the SKOS-Core schema [SKOS GUIDE] [SKOS SCHEMA] to express additional semantics and constraints on the SKOS data model.

The SKOS model is an abstract data model defining the structure of a thesaurus. The SKOS-Core 1.0 schema is an encoding of this model as an RDF schema [RDFS]. Some semantics and constraints present in the data model cannot be expressed by RDF schema alone, but require features of OWL. These are described here. Also, some semantics and constraints cannot be expressed by either RDFS or OWL, and these are also described.

2. OWL Features of SKOS-Core 1.0   [back to contents]

The following properties are declared to be of type owl:TransitiveProperty:

The following property pairs are declared to be each other's inverse, via a statement using the owl:inverseOf predicate:

The following properties are declared to be of type owl:SymmetricProperty:

3. Constraints and Semantics Not Expressable With RDFS or OWL   [back to contents]

References

[SKOS GUIDE]
SKOS-Core 1.0 Guide. Miles, A.J., Rogers, R., Beckett, D. SWAD-Europe Thesaurus Activity.
http://www.w3.org/2001/sw/Europe/reports/thes/1.0/guide/

[SKOS SCHEMA]
SKOS-Core 1.0 RDF Schema. Miles, A.J., Rogers, R., Beckett, D. SWAD-Europe Thesaurus Activity.
http://www.w3.org/2004/02/skos/core.rdf

[OWL]
OWL Web Ontology Language Guide. Smith, M.K., Welty, C., McGuiness, D.L. Eds. W3C Recommendation.
http://www.w3.org/TR/owl-guide/

[RDFS]
RDF Vocabulary Description Language 1.0: RDF Schema. Brickley, D., Guha, R.V. Eds. W3C Recommendation.
http://www.w3.org/TR/rdf-schema/

Appendix: SKOS-Core 1.0 Schema (02/06/2004)

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE rdfs [
	<!ENTITY rdf "http://www.w3.org/1999/02/22-rdf-syntax-ns#">
	<!ENTITY rdfs "http://www.w3.org/2000/01/rdf-schema#">
	<!ENTITY dc "http://purl.org/dc/elements/1.1/">
	<!ENTITY dct "http://purl.org/dc/terms/">
	<!ENTITY foaf "http://xmlns.com/foaf/0.1/">
	<!ENTITY owl "http://www.w3.org/2002/07/owl#">
]>
<rdf:RDF xml:base="http://www.w3.org/2004/02/skos/core" xmlns:rdf="&rdf;" xmlns:rdfs="&rdfs;" xmlns:dc="&dc;" xmlns:dct="&dct;" xmlns:owl="&owl;">
	<!-- This schema is described by the SKOS-Core 1.0 Guide, which can be found at http://www.w3.org/2001/sw/Europe/reports/thes/1.0/guide/ -->
	<!-- Description of this schema -->	
	<rdf:Description rdf:about="">
		<dc:title>SKOS-Core 1.0</dc:title>
		<dc:description>An RDF schema for encoding simple concept schemes such as thesauri and subject heading schemes.</dc:description>
		<dc:creator>Alistair Miles</dc:creator>
		<dc:creator>Nikki Rogers</dc:creator>
		<dc:creator>Dave Beckett</dc:creator>
		<dct:modified>2004-03-26</dct:modified>
	</rdf:Description>
	<!-- Fundamental classes -->
	<rdfs:Class rdf:ID="ConceptScheme">
		<rdfs:label>Concept Scheme</rdfs:label>
		<rdfs:comment>A concept scheme is a collection of concepts.</rdfs:comment>
	</rdfs:Class>
	<rdfs:Class rdf:ID="Concept">
		<rdfs:label>Concept</rdfs:label>
		<rdfs:comment>A concept is any unit of thought that can be defined or described.</rdfs:comment>
	</rdfs:Class>
	<rdfs:Class rdf:ID="TopConcept">
		<rdfs:label>Top Concept</rdfs:label>
		<rdfs:comment>A concept that sits at the top of the concept hierarchy.</rdfs:comment>
    <rdfs:subClassOf rdf:resource="#Concept"/>
	</rdfs:Class>	
	<!-- Basic properties of concepts -->
	<rdf:Property rdf:ID="inScheme">
		<rdfs:label>in scheme</rdfs:label>
		<rdfs:subPropertyOf rdf:resource="&rdfs;isDefinedBy"/>
		<rdfs:domain rdf:resource="#Concept"/>
		<rdfs:range rdf:resource="#ConceptScheme"/>
		<rdfs:comment>Use this property to state that a concept is a part of some concept scheme.  A concept may be a part of more than one scheme.</rdfs:comment>
	</rdf:Property>
	<rdf:Property rdf:ID="prefLabel">
		<rdfs:label>preferred label</rdfs:label>
		<rdfs:subPropertyOf rdf:resource="&rdfs;label"/>
		<rdfs:comment>Use this property to indicate a preferred label for a resource.  If the resource is a concept in some conceptual scheme, then it is strongly recommended that the preferred label be a unique label within that scheme.</rdfs:comment>
	</rdf:Property>
	<rdf:Property rdf:ID="altLabel">
		<rdfs:label>alternative label</rdfs:label>
		<rdfs:subPropertyOf rdf:resource="&rdfs;label"/>
		<rdfs:comment>Use this property to indicate an alternative (non-preferred) label for a resource.</rdfs:comment>
	</rdf:Property>
	<rdf:Property rdf:ID="prefSymbol">
		<rdfs:label>preferred symbol</rdfs:label>
		<rdfs:domain rdf:resource="&rdf;Resource"/>
		<rdfs:range rdf:resource="&foaf;Image"/>
		<rdfs:comment>Use this property to indicate a preferred symbolic representation for a resource.</rdfs:comment>
	</rdf:Property>
	<rdf:Property rdf:ID="altSymbol">
		<rdfs:label>alternative symbol</rdfs:label>
		<rdfs:domain rdf:resource="&rdf;Resource"/>
		<rdfs:range rdf:resource="&foaf;Image"/>
		<rdfs:comment>Use this property to indicate an alternative (non-preferred) symbolic representation for a resource.</rdfs:comment>
	</rdf:Property>
	<rdf:Property rdf:ID="externalID">
		<rdfs:label>identifier</rdfs:label>
		<rdfs:subPropertyOf rdf:resource="&rdf;value"/>
		<rdfs:domain rdf:resource="#Concept"/>
		<rdfs:comment>Use or extend this property to indicate any non-URI code that is used to uniquely identify a concept within a conceptual scheme.</rdfs:comment>
	</rdf:Property>
	<rdf:Property rdf:ID="semanticRelation">
		<rdfs:label>semantic relation</rdfs:label>
		<rdfs:domain rdf:resource="#Concept"/>
		<rdfs:range rdf:resource="#Concept"/>
		<rdfs:comment>This is the super-property of all properties used to make statements about how concepts within the same conceptual scheme relate to each other.</rdfs:comment>
	</rdf:Property>
	<!-- Basic semantic relation properties -->
	<rdf:Property rdf:ID="broader">
		<rdfs:label>has broader</rdfs:label>
		<rdf:type rdf:resource="&owl;TransitiveProperty"/>
		<rdfs:subPropertyOf rdf:resource="#semanticRelation"/>
		<rdfs:comment>This property carries weak semantics.  It may be used to state that the object is in some way more general in meaning than the subject.  Essentially it provides a means of organising concepts into a hierarchy (tree), without being restrictive about the exact semantic implications of the hierarchical structure itself.  Extend this property to create properties that carry stronger semantics, but may be reduced to a hierarchical structure for simple visual displays.</rdfs:comment>
	</rdf:Property>
	<rdf:Property rdf:ID="narrower">
		<rdfs:label>has narrower</rdfs:label>
		<rdf:type rdf:resource="&owl;TransitiveProperty"/>
		<rdfs:subPropertyOf rdf:resource="#semanticRelation"/>
		<owl:inverseOf rdf:resource="#broader"/>
		<rdfs:comment>This property is the inverse of the 'broader' property.</rdfs:comment>
	</rdf:Property>
	<rdf:Property rdf:ID="related">
		<rdfs:label>related to</rdfs:label>
		<rdf:type rdf:resource="&owl;SymmetricProperty"/>
		<rdfs:subPropertyOf rdf:resource="#semanticRelation"/>
		<rdfs:subPropertyOf rdf:resource="&rdfs;seeAlso"/>
		<rdfs:comment>This property carries weak semantics.  It may be used to state that that the object is in some way related to the subject, and the relationship is NOT to be treated as hierarchical.  Essentially it provides a means of linking concepts in different branches of a hierarchy (tree).  Extend this property to create properties with stronger semantics, but may still be reduced to an associative structure for simple visual display.</rdfs:comment>
	</rdf:Property>
	<!-- Semantic relation property extensions -->
	<rdf:Property rdf:ID="broaderInstantive">
		<rdfs:label>instance of</rdfs:label>
		<rdfs:subPropertyOf rdf:resource="#broader"/>
		<rdfs:subPropertyOf rdf:resource="&rdf;type"/>
		<rdfs:comment>An extension of the 'broader' property to specify the instantiation (instance of) relationship between two concepts.  This property is semantically equivalent to the 'rdf:type' property.</rdfs:comment>
	</rdf:Property>
	<rdf:Property rdf:ID="narrowerInstantive">
		<rdfs:label>has instance</rdfs:label>
		<rdfs:subPropertyOf rdf:resource="#narrower"/>
		<owl:inverseOf rdf:resource="#broaderInstantive"/>
		<rdfs:comment>This property is the inverse of the 'broaderInstantive' property.</rdfs:comment>
	</rdf:Property>
	<rdf:Property rdf:ID="broaderGeneric">
		<rdfs:label>sub-class of</rdfs:label>
		<rdf:type rdf:resource="&owl;TransitiveProperty"/>
		<rdfs:subPropertyOf rdf:resource="#broader"/>
		<rdfs:subPropertyOf rdf:resource="&rdfs;subClassOf"/>
		<rdfs:comment>An extension of the 'broader' property to specify the class subsumption (sub-class/super-class) relationship between two concepts.  This property is semantically equivalent to the 'rdfs:subClassOf' property.</rdfs:comment>
	</rdf:Property>
	<rdf:Property rdf:ID="narrowerGeneric">
		<rdfs:label>super-class of</rdfs:label>
		<rdf:type rdf:resource="&owl;TransitiveProperty"/>
		<rdfs:subPropertyOf rdf:resource="#narrower"/>
		<owl:inverseOf rdf:resource="#broaderGeneric"/>
		<rdfs:comment>This property is the inverse of the 'broaderGeneric' property.</rdfs:comment>
	</rdf:Property>
	<rdf:Property rdf:ID="broaderPartitive">
		<rdfs:label>part of</rdfs:label>
		<rdf:type rdf:resource="&owl;TransitiveProperty"/>
		<rdfs:subPropertyOf rdf:resource="#broader"/>
		<rdfs:subPropertyOf rdf:resource="&dct;isPartOf"/>
		<rdfs:comment>An extension of the 'broader' property to specify a partitive (part of) relationship between two concepts.</rdfs:comment>
	</rdf:Property>
	<rdf:Property rdf:ID="narrowerPartitive">
		<rdfs:label>has part</rdfs:label>
		<rdf:type rdf:resource="&owl;TransitiveProperty"/>
		<rdfs:subPropertyOf rdf:resource="#narrower"/>
		<rdfs:subPropertyOf rdf:resource="&dct;hasPart"/>
		<owl:inverseOf rdf:resource="#broaderPartitive"/>
		<rdfs:comment>This property is the inverse of the 'broaderPartitive' property.</rdfs:comment>
	</rdf:Property>
	<rdf:Property rdf:ID="relatedPartOf">
		<rdfs:label>part of</rdfs:label>
		<rdf:type rdf:resource="&owl;TransitiveProperty"/>
		<rdfs:subPropertyOf rdf:resource="#related"/>
		<rdfs:subPropertyOf rdf:resource="&dct;isPartOf"/>
		<rdfs:comment>An extension of the 'related' property.  Use this property to express a partitive relationship between concepts, where it is desired that such a relationship be treated as associative (i.e. linking separate branches of a hierarchy) and NOT hierarchical.</rdfs:comment>
	</rdf:Property>
	<rdf:Property rdf:ID="relatedHasPart">
		<rdfs:label>has part</rdfs:label>
		<rdf:type rdf:resource="&owl;TransitiveProperty"/>
		<rdfs:subPropertyOf rdf:resource="#related"/>
		<rdfs:subPropertyOf rdf:resource="&dct;hasPart"/>
		<owl:inverseOf rdf:resource="#relatedPartOf"/>
		<rdfs:comment>This property is the inverse of the 'relatedPartOf' property.</rdfs:comment>
	</rdf:Property>	
	<!-- Scope notes, definitions and examples -->
	<rdf:Property rdf:ID="scopeNote">
		<rdfs:label>scope note</rdfs:label>
		<rdfs:subPropertyOf rdf:resource="&rdfs;comment"/>
		<rdfs:comment>A scope note is a piece of text that in some way helps to elucidate the intended meaning of a concept.</rdfs:comment>
		<rdfs:domain rdf:resource="#Concept"/>
	</rdf:Property>
	<rdf:Property rdf:ID="definition">
		<rdfs:label>definition</rdfs:label>
		<rdfs:subPropertyOf rdf:resource="&rdfs;comment"/>
		<rdfs:comment>A formal (dictionary style) definition of the intended meaning of a concept.</rdfs:comment>
		<rdfs:domain rdf:resource="#Concept"/>
	</rdf:Property>
	<rdf:Property rdf:ID="example">
		<rdfs:label>example</rdfs:label>
		<rdfs:subPropertyOf rdf:resource="&rdfs;comment"/>
		<rdfs:comment>A contextual example of the use of a concept, that helps to elucidate its intended meaning.</rdfs:comment>
		<rdfs:domain rdf:resource="#Concept"/>
	</rdf:Property>
	<!-- N.B. use the foaf:depiction property to attach an image depicting a concept. -->
</rdf:RDF>