Hi, my intention is to extend one entity bean from another using the JOINED stategey. I have a very simple setup, which produces the following exception: jectName: persistence.units:ear=calc.ear,jar=calc.jar,unitName=userDatabase State: FAILED Reason: org.hibernate.AnnotationException: Unable to define/override @Id(s) on a subclass: de.test.Client I Depend On: jboss.jca:service=ManagedConnectionFactory,name=calcDS Depends On Me: jboss.j2ee:ear=calc.ear,jar=calc.jar,name=RegisterAction,service=EJB3 Here is the source code of the two entity beans: @Entity @Inheritance(strategy= InheritanceType.JOINED) public class Person { @Id public String lastname; String firstName; String street; String zipcode; String city; String country; String phone; ... } @Entity public class Client extends Person { @Id String hostname; String email; String customernumber; ... } Why is this not working? View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3987230#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...