function validateMetadata($label, &$md)
 {
     $valid = false;
     $mdFactory = new Docman_MetadataFactory($this->groupId);
     if ($mdFactory->isValidLabel($label)) {
         $_md =& $mdFactory->getFromLabel($label);
         if ($_md !== null && $_md->getGroupId() == $this->groupId) {
             $valid = true;
             $md = $_md;
         }
     }
     return $valid;
 }