When I define a 1:1 bidirectional relationship, create two such related objects, and then delete the object that doesn't have the FK in its class table, it will silently be removed from the relationship before being deleted. That's happens even though I specified delete-action="restricted" on the FK.

Expected behaviour would be the FK constraint being violated upon deletion of the object.

Please see thread "deletePersistent() automatically nulling out referring FKs?!" on mailinglist jdo-dev for details.