RDQL and OWL

Hi All,
I'm new to RDF and I'm trying to asses the feasibility of using OWL for
a product I'm developing.
I would like to know if being:

A a metaclass
B a subclass of A
C a subclass of A
D a subclass of B

How can i write an RDQL query saying that I wants to retrieve all the
instances of A?
And will the query understand my ontology and will it return instances
of B, C, D as well?

Thanks

Alessandro