public function getFlowURI($flow_name, array $params = array()) {
        if (empty($flow_name)) {
            throw new VGS_Client_Exception("Unspecified flow name");
        }

        $default_params = array(
            'client_id' => $this->getClientID(),
            'response_type' => 'code',
            'redirect_uri' => $this->getCurrentURI(),
        );

        if ($this->xiti) {
            $default_params['xiti_json'] = $this->getXitiConfiguration();
        }
        $default_params['v'] = self::VERSION;

        $parameters = array_merge($default_params, $params);
        return $this->getUrl('flow', $flow_name, $parameters);
    }