protected function mmTable($conf, $key, $fConf=null) {
		if (!isset($conf['refTable'])) {
			// compute mm table name
			$mmTable = isset($conf[2]) ? $conf[2] :
				static::getMMTableName($conf['relTable'],
					$conf['relField'], $this->table, $key, $fConf);
			$this->fieldConf[$key]['has-many']['refTable'] = $mmTable;
		} else
			$mmTable = $conf['refTable'];
		return $mmTable;
	}