static function init()
    {
        if (self::$initialized == false) {
            self::$NONE = new Permission(1, "none");
            self::$SOI = new Permission(2, "soi");
            self::$COI = new Permission(3, "coi");
            self::$DOI = new Permission(4, "doi");
            self::$DOI_PLUS = new Permission(5, "doi+");
            self::$OTHER = new Permission(6, "other");
            self::$initialized = true;
        }
    }