private static function _oidReverseMap(): array
    {
        static $map;
        if (!isset($map)) {
            $map = array();
            // for eatch attribute type
            foreach (self::MAP_OID_TO_NAME as $oid => $names) {
                // for primary name and aliases
                foreach ($names as $name) {
                    $map[strtolower($name)] = $oid;
                }
            }
        }
        return $map;
    }