public static function validate($instance, $group = "") {
		$class = get_class ( $instance );
		$cache = self::getClassCacheValidators ( $class, $group );
		if ($cache !== false) {
			return self::validateFromCache_ ( $instance, $cache );
		}
		$members = self::fetch ( $class );
		if ($group !== "") {
			$members = self::getGroupArrayValidators ( $members, $group );
		}
		return self::validate_ ( $instance, $members );
	}