public function indexAction()
    {
        $navigation = $this->getServiceLocator()
                           ->get( 'Grid\Menu\Model\Menu\Model' )
                           ->findNavigation();

        $view = new ViewModel( array(
            'navigation' => $navigation,
        ) );

        $this->getResponse()
             ->getHeaders()
             ->addHeaderLine( 'Content-Type', 'application/xml' );

        return $view->setTerminal( true );
    }