public function getXmlByRdfItem(core_kernel_classes_Resource $item, $language = '')
    {
        $itemService = taoItems_models_classes_ItemsService::singleton();

        //check if the item is QTI item
        if (! $itemService->hasItemModel($item, array(ItemModel::MODEL_URI))) {
            throw new common_Exception('Non QTI item('.$item->getUri().') opened via QTI Service');
        }

        $file = $itemService->getItemDirectory($item, $language)->getFile(self::QTI_ITEM_FILE);
        return $file->read();
    }