protected function addTarget(CNabuSiteTarget $nb_site_target, $default = false)
    {
        $nb_site = $this->nb_engine->getHTTPServer()->getSite();
        if ($nb_site instanceof CNabuSite) {
            return $nb_site->addTarget($nb_site_target, $default);
        } else {
            throw new ENabuCoreException(ENabuCoreException::ERROR_SITE_NOT_INSTANTIATED);
        }
    }