Rdfs:subClassOf
From semanticweb.org
This semantic relation, on this wiki annotated with the property Property:Subclass of, declares that the class derives from another. Multiple inheritance is possible.
SMW's RDF Export uses rdfs:subClassOf to represent a MediaWiki subcategory, that is, when a category itself has a Category.
(old sample RDF output:)
<rdfs:Class rdf:ID="Opera"> <rdfs:subClassOf rdf:resource="#MusicalWork" /> </rdfs>
<owl:Class rdf:ID="Opera"> <rdfs:subClassOf rdf:resource="#MusicalWork" /> </owl:Class>