public static function add($groupname, $document_id, $rights = TlonRights::READ_WRITE, $groupinfo = '')
 {
     if (!TlonGroup::exists($groupname)) {
         if (!TlonGroup::add($groupname, $groupinfo)) {
             return false;
         }
     }
     return TlonData::insert(self::$TABLE, array($groupname, $document_id, $rights));
 }
 public static function add($username, $groupname, $rights = TlonRights::READ_WRITE, $groupinfo = '')
 {
     if (!TlonGroup::exists($groupname)) {
         if (!TlonGroup::add($groupname, $groupinfo)) {
             return false;
         }
     }
     if (self::getByUsernameGroupname($username, $groupname)) {
         return self::edit($username, $groupname, $rights);
     } else {
         return TlonData::insert(self::$TABLE, array($username, $groupname, $rights));
     }
 }