[hibernate-dev] JPA 2 spec excerpts about @PrimaryKeyJoinColumn and derived identities

I'm sending these excerpts separately, rather than cluttering up Emmanuel's thread. Regards, Gail 11.1.40 PrimaryKeyJoinColumn Annotation The PrimaryKeyJoinColumn annotation specifies a primary key column that is used as a foreign key to join to another table. The PrimaryKeyJoinColumn annotation is used to join the primary table of an entity subclass in the JOINED mapping strategy to the primary table of its superclass; it is used within a SecondaryTable annotation to join a secondary table to a primary table; and it may be used in a OneToOne mapping in which the primary key of the referencing entity is used as a foreign key to the referenced entity[108]. Footnote [108]: The derived id mechanisms described in section 2.4.1.1 are now to be preferred over PrimaryKeyJoinColumn for the OneToOne mapping case. 2.4.1 Primary Keys Corresponding to Derived Identities The identity of an entity may be derived from the identity of another entity (the "parent" entity) when the former entity (the "dependent" entity) is the owner of a many-to-one or one-to-one relationship to the parent entity and a foreign key maps the relationship from dependent to parent. If a many-to-one or one-to-one entity relationship corresponds to a primary key attribute, the entity containing this relationship cannot be persisted without the relationship having been assigned an entity since the identity of the entity containing the relationship is derived from the referenced entity.[12]