private function _getApiUri($hostname, $storeId, $major, $minor)
    {
        return sprintf(
            Radial_Core_Helper_Data::URI_FORMAT,
            $hostname,
            $major,
            $minor,
            $storeId,
            self::AD_VAL_SERVICE,
            self::AD_VAL_OPERATION,
            '',
            'xml'
        );
    }