/**
  * append a datarow object to the list
  * @param DataRow $data
  * @return boolean false if data table not match
  */
 public function append(DataRow $data)
 {
     if ($data->getTable()) {
         if ($data->getTable()->getTableName() != $this->_table->getTableName()) {
             return false;
         }
     } else {
         $data->setTable($this->_table);
     }
     $this->_data[] = $data;
     return true;
 }