A property with the following URI has been added to the SKOS Core Vocabulary:
http://www.w3.org/2004/02/skos/core#subjectIndicator
For a summary of this property, see:
http://www.w3.org/2004/02/skos/core/spec/#subjectIndicator
The skos:subjectIndicator property has been added to support the subject indicator mechanism for establishing the identity of a 'subject' (read 'resource' in RDF speak). This property is an inverse-functional property, allowing it to be used as a basis for resource identification.
So for example, it would quite reasonable to publish an RDF description of a concept without an assigned URI, e.g.
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:skos="http://www.w3.org/2004/02/skos/core#">
<skos:Concept>
<skos:prefLabel xml:lang="en">Iraq</skos:prefLabel>
<skos:subjectIndicator rdf:resource="http://psi.oasis-open.org/geolang/iso3166/#368"/>
</skos:Concept>
</rdf:RDF>
... and then reference this concept within an RDF description of another resource using the skos:subjectIndicator property, e.g.
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:skos="http://www.w3.org/2004/02/skos/core#">
<rdf:Description rdf:about="http://www.iraqdaily.com/">
<skos:subject rdf:parseType="Resource">
<skos:subjectIndicator rdf:resource="http://psi.oasis-open.org/geolang/iso3166/#368"/>
</skos:subject>
</rdf:Description>
</rdf:RDF>