protected function _acceptAcl(NavigationPage $page)
 {
     if (!($acl = $this->getAcl())) {
         // no acl registered means don't use acl
         return true;
     }
     $role = $this->getRole();
     $resource = $page->getResource();
     $privilege = $page->getPrivilege();
     if ($resource || $privilege) {
         // determine using helper role and page resource/privilege
         return $acl->isAllowed($role, $resource, $privilege);
     }
     return true;
 }