function openid_associate($request)
    {
        $assoc_type = $request->assoc_type;
        $session_type = $request->session->session_type;
        if ($this->negotiator->isAllowed($assoc_type, $session_type)) {
            $assoc = $this->signatory->createAssociation(false,
                                                         $assoc_type);
            return $request->answer($assoc);
        } else {
            $message = sprintf('Association type %s is not supported with '.
                               'session type %s', $assoc_type, $session_type);
            list($preferred_assoc_type, $preferred_session_type) =
                $this->negotiator->getAllowedType();
            return $request->answerUnsupported($message,
                                               $preferred_assoc_type,
                                               $preferred_session_type);
        }
    }