protected function getAcl($oid = null, $entriesInheriting = true)
 {
     static $id = 1;
     if ($oid === null) {
         $oid = new ObjectIdentity($this->context->getObject()->getId(), get_class($this->context->getObject()));
     }
     return new Acl($id++, $oid, $this->strategy, array(), $entriesInheriting);
 }