@Override
 public void notifyChanged(Notification notification) {
   super.notifyChanged(notification);
   if (notification.getNotifier() instanceof Simple) {
     switch (notification.getFeatureID(Simple.class)) {
       case PrfPackage.SIMPLE__ID:
         updateSimpleRefID(notification);
         break;
       default:
         break;
     }
   } else if (notification.getNotifier() instanceof Struct) {
     switch (notification.getFeatureID(Struct.class)) {
       case PrfPackage.STRUCT__SIMPLE:
         updateSimpleRefs(notification);
         break;
       default:
         break;
     }
   }
 }