This empty class is the common root for all persistent capable classes. If
this class inherits from java.lang.Object then all subclasses are
serializable with the standard Java serialization mechanism. If this class
inherits from com.objy.db.app.ooObj then all subclasses are
additionally serializable with the Objectivity ODBMS persistance
mechanism. Thus, by modifying the inheritance of this class the entire tree
of subclasses can be switched to Objectivity compatibility (and back) with
minimum effort.