I had the very same question but no one seems to have seen my post to answer me. From everything that I read in the online manual about CMP, it doesn't look like JBoss' implementation of CMP allows for defining foreign key relationships, nor compound indexes on fields. In other words, it's not a full replacement for SQL DDL.
Castor (http://castor.exolab.org) on the other hand does have all those features. Castor can be used as an O/R mapping API with JBoss when used in BMP mode.
no it does not, as this will be part of CMP 2.0, which is not implemented in jboss 2.2.2
Dan O'Connor a contributor to the codebase of JBoss has created supplemental software that will allow you t develop EJB CMP2.0 code for Jboss. His company can be found at www.mvcsoft.com. I use the product and it works well.
jboss supports many-to-many, one-to-one and one-to-many relationships, but it's in the development stage.
Project Rabbit Hole will include it, but it doesn't have a release date so don't ask about it.