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.