/** {@inheritDoc} */
 public int getMaximumTreeRank(int productId) {
   Criteria rootFilter = getRootStoryCriteria(productId);
   rootFilter.addOrder(Order.desc("treeRank"));
   rootFilter.setMaxResults(1);
   Story story = (Story) uniqueResult(rootFilter);
   if (story == null) {
     return 0;
   } else {
     return story.getTreeRank();
   }
 }