How can I do downcasting in HQL? For example, suppose that I have a query with 2 where clauses C1 and C2 like

from A a where C1 & C2

if
1- I know that all "a" objects that satisfy C1 are of type B (which is a cubclass of A)

2- I need to use a field defined in B in C2 clause of my query.

For this, I need ot downcast "a" objects to type B to be able to write clause C2. How can I do that?

Thanks,
MH