public static function fromXML($xml)
    {
        $dom = new DOMDocument();
        $dom->loadXML($xml);
        $xpath = new DOMXPath($dom);
        $xpath->registerNamespace('a', self::getNamespace());
        $response = $xpath->query('//a:CaptureNotification');
        if ($response->length == 1) {
            return 
                new OffAmazonPaymentsNotifications_Model_CaptureNotification(
                    $response->item(0)
                );
        } else {
            throw new Exception(
                "Unable to construct " .
                "OffAmazonPaymentsNotifications_Model_CaptureNotification" .
                "from provided XML. Make sure that CaptureNotification" .
                "is a root element"
            );
        }
    }