protected function unmarshall(DOMElement $element)
    {
        if (($identifier = $this->getDOMElementAttributeAs($element, 'identifier', 'string')) !== null) {
            $object = new MapResponsePoint($identifier);

            return $object;
        } else {
            $msg = "The mandatory attribute 'identifier' is missing from element '" . $element->localName . "'.";
            throw new UnmarshallingException($msg, $element);
        }
    }