protected function readMessageDefaults(\SimpleXMLElement $message): array
    {
        // init
        $defaults = [];

        /* @var \SimpleXMLElement $defaultValueNode */
        foreach ($message->defaults[0] ?? [] as $defaultValueNode) {
            $attributes = $defaultValueNode->attributes();
            $id = (string)$attributes->id;
            $defaults[$id] = (string)$attributes->value;
        }

        return $defaults;
    }