Best practice for multiple Hibernate configurations

Hello!

I see that Hibernate/JPA are very well integratet with dm server. But I
was wondering what is the best practice when multiple modules use
Hibernate whose data models overlap?

An Example: I have two models using the "User" entity. Up to now, I
have to declare it in both modules' hbm.xml because the don't share
a common session context.

The reason I'd like to this, is that I want to have parts of the application
pluggable although those (optional) parts use certain "core" entities.

Can anyone give some information on that?

Cheers,

Fabian