trying to map a legacy db (sybase, why?), I encountered the following concern:
discriminator is used couple of times along the inheritance, fetched using a formula (sql select something). I don't want to requery using that formula, but to reference that discriminator on the parent.

more detailed:
entitiy A has a discriminator 'Ad' fetched using a formula from another table.
B is a composite of A.
both A,B are not concrete, but C,D respectivly (C inherits A,D inherits B)
thus D is a composite of C, when C is discriminated using 'Ad'.

I want D to be discriminated also using 'Ad', the same way C is, without rewrinting the formula (which might be an expansive sql query) but referencing it from A.

How? have I missed something simple?
/Ron