protected function _construct()
 {
     parent::_construct();
     $defaultData = Mage::getConfig()->getNode(self::XML_PATH_DEFAULT_DATA);
     if ($defaultData) {
         foreach ($defaultData->children() as $item) {
             if (!isset($item->entity_id)) {
                 continue;
             }
             $entityId = (string) $item->entity_id;
             $this->_defaultData[$entityId] = array();
             foreach ($item->children() as $value) {
                 $this->_defaultData[$entityId][$value->getName()] = (string) $value;
             }
         }
     }
     $this->_restoreTables[] = $this->getTable('catalog/category');
     foreach (array('datetime', 'decimal', 'int', 'text', 'varchar') as $suffix) {
         $this->_restoreTables[] = $this->getTable(array('catalog/category', $suffix));
     }
 }