Hello, Having tried various experiments and 'googled' all over the place, I'm unable to create two entities that create a one for one join which when reversed engineered into an ERD tool (eg. MySQL Workbench) shows up with the correct notation (i.e. a one to one join). The scenario... EntityA has a compound primary key (two fields) and various other non-key fields. EntityA can be associated with zero or one EntityB objects (but no more). EntityB has one non-key field. For each EntityB there must be one and only one EntityA. I don't want EntityB to have its own primary key. How can I annotate both EntityA and EntityB to ensure the above cardinality and correct reverse engineering in a data modeling tool? Thanks, Matthew View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3985175#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...