public static PositionHolder getPosition(XModelObject object, String attribute) {
   String id =
       (attribute == null)
           ? POSITION_HOLDER_ID
           : POSITION_HOLDER_ID + "." + attribute; // $NON-NLS-1$
   PositionHolder h = (PositionHolder) object.getObject(id);
   if (h == null) {
     h = new PositionHolder(object, attribute);
     object.setObject(id, h);
   }
   return h;
 }