Some comments on EJB 3.0 PFD

In a previous post, I complained about lack of clarity in the specification of the @IdClass annotation. Well, it seems that this lack of clarity extends to anything to do with composite primary keys. Here is what the specification has to say about composite primary keys:

Composite primary keys typically arise when mapping from legacy databases when the database key is comprised of several columns.

Perhaps this explains why there aren't any real examples to show how Entity relationships ought to be mapped when composite primary keys are involved.