As an implementation for the object relational mapping is chosen for Hibernate.
An implementation design decission has been to decide for xml mapping files. Are annotation been considered?
heikki : I prefer having the O/R binding definition in XML files rather than inside the Java source code; I find it easier to find what you look for that way, and it is a bit more 'decoupled' in my opinion. But it's basically just a matter of taste, and I'm OK with using annotations if that is what everybody else prefers.
Note that the current implementation does not use annotations; if we switch to that style we'll have to update the current code base.