Need your help for writing OWL based ontology/knowledge base.

Hey,

I got a problem when writing the OWL based ontology. But I do not find how
to solve it. I may need your help.

The problem is that:

I want to define tow class, For instance: owl:class Topic and owl:class
Researcher:

There are three instances of the Topic class, namely knowledgeDiscovery,
dataMining, textMining.
three instance of the Research class, namely A, B, C,

dataMining and textMining are subtopic of knowledgeDiscovery.
A workIn knowledge discovery, B workIn dataMining, and C workIn textMining.

Now, I have a query "SELECT ?Researcher WHERE ?Research workIn
knowledgeDiscovery",
I hope the three tuples will be extracted. They are "A workIn
knowledgeDiscovery", "B workIn knowledgDiscovery", and "C workIn
knowledgeDiscovery".

How can i define the subtopic relation in the knowledge base so that i can
get the above results. The subtopic relation is similar to the
rdfs:subClassOf. However, it works on the
instances only.

Thanks for your reply

regards
Jason