public static function get_subwiki_files_parameters() {
        return new external_function_parameters (
            array(
                'wikiid' => new external_value(PARAM_INT, 'Wiki instance ID.'),
                'groupid' => new external_value(PARAM_INT, 'Subwiki\'s group ID, -1 means current group. It will be ignored'
                                        . ' if the wiki doesn\'t use groups.', VALUE_DEFAULT, -1),
                'userid' => new external_value(PARAM_INT, 'Subwiki\'s user ID, 0 means current user. It will be ignored'
                                        .' in collaborative wikis.', VALUE_DEFAULT, 0)
            )
        );
    }