RDF schema for topics

<rdfs:Class rdf:about="http://www.w3.org/2002/01/bookmark#Topic">
    <rdfs:label>Topic</rdfs:label>
    <rdfs:comment>for cataloguing resources under topics</rdfs:comment>
</rdfs:Class>

<rdfs:Property rdf:about="http://www.w3.org/2002/01/bookmark#subTopicOf"> 
    <rdfs:label>subTopic</rdfs:label>
    <rdfs:comment>defines a hierarchical relationship
      between topics</rdfs:comment>
</rdfs:Property>