private function getTargetNS($xpath)
    {
        $query   = "//*[local-name()='schema' and namespace-uri()='http://www.w3.org/2001/XMLSchema']/@targetNamespace";
        $targetNs =  $xpath->query($query);

        if ($targetNs) {
            foreach ($targetNs as $entry) {
                return $entry->nodeValue;
            }
        }
    }