This is pretty much done. The only identifier-related piece to do still is support for @MapsId. Part of this process was introducing the notion of synthetic attributes, which are attributes which don't really exist in the domain classes. HIbernate uses them for a number of things. Here, it was needed for handling "non-aggregated composite identifiers" (composite ids that are not represented by a @EmbeddedId). The important take away is that in the metamodel now identifiers ALWAYS are represented as a single attribute. In the case of org.hibernate.id.EntityIdentifierNature#SIMPLE and org.hibernate.id.EntityIdentifierNature#AGGREGATED_COMPOSITE that single attribute is a real attribute; in the case of org.hibernate.id.EntityIdentifierNature#COMPOSITE the attribute is synthetic. On Wed 11 Apr 2012 04:03:22 PM CDT, Steve Ebersole wrote: -- steve(a)hibernate.org http://hibernate.org