/** {@inheritDoc} */
 public void removeObject(ObjectData object) {
   storage.children.get(getObjectId()).remove(object.getObjectId());
   storage.parents.get(object.getObjectId()).remove(getObjectId());
   if (storage.parents.get(object.getObjectId()).size() == 0) {
     storage.unfiled.add(object.getObjectId());
   }
   storage.indexListener.updated(object);
 }
 /** {@inheritDoc} */
 public void addObject(ObjectData object) throws ConstraintException {
   storage.children.get(getObjectId()).add(object.getObjectId());
   storage.parents.get(object.getObjectId()).add(getObjectId());
   storage.unfiled.remove(object.getObjectId());
   storage.indexListener.updated(object);
 }