public function map($format, $value)
 {
     switch ($format) {
         case "username":
             $user = User::findOneByUsername($value);
             if ($user) {
                 return $user->getId();
             }
             break;
         case "email":
             $user = User::findOneByEmail($value);
             if ($user) {
                 return $user->getId();
             }
             break;
         default:
             //Datenfeld:
             $datafield = DataField::find($format);
             if ($datafield && $datafield['object_type'] === "user") {
                 $entry = DatafieldEntryModel::findOneBySQL("datafield_id = ? AND content = ?", array($datafield->getId(), $value));
                 if ($entry) {
                     return $entry['range_id'];
                 }
             }
     }
 }