protected static function get_note_structure() {
        return array(
                     'id'           => new external_value(PARAM_INT, 'id of this note'),
                     'courseid'     => new external_value(PARAM_INT, 'id of the course'),
                     'userid'       => new external_value(PARAM_INT, 'user id'),
                     'content'      => new external_value(PARAM_RAW, 'the content text formated'),
                     'format'       => new external_format_value('content'),
                     'created'      => new external_value(PARAM_INT, 'time created (timestamp)'),
                     'lastmodified' => new external_value(PARAM_INT, 'time of last modification (timestamp)'),
                     'usermodified' => new external_value(PARAM_INT, 'user id of the creator of this note'),
                     'publishstate' => new external_value(PARAM_ALPHA, "state of the note (i.e. draft, public, site) ")
        );
    }