public function get_aggregation_method($criteriatype = 0) {
        global $DB;
        $params = array('badgeid' => $this->id, 'criteriatype' => $criteriatype);
        $aggregation = $DB->get_field('badge_criteria', 'method', $params, IGNORE_MULTIPLE);

        if (!$aggregation) {
            return BADGE_CRITERIA_AGGREGATION_ALL;
        }

        return $aggregation;
    }