Query of individuals that "May" belong to a class

Hi, i wonder to retrieve in my knowledge base all the individuals that 
"May" belong to a class. For instance, given a property prop P and 
another class C, all the individuals that do not have an instance of C 
as P role filler.  Say this class D because of the open world 
assumpition, I think that we are not able to retrieve all the 
individuals in the KB that "colud" belong to D. Some ideas? Epistemic 
Operators could help?

I'm using Jena + Pellet.

thanks in advance,
Cristiano Longo