protected function _serializeRootAttributes()
	{
		$rootAttributes = $this->_getRootAttributes();
		$qualifyAttributes = function ($name) use ($rootAttributes) {
			return sprintf('%s="%s"', $name, $rootAttributes[$name]);
		};
		$qualifiedAttributes = array_map($qualifyAttributes, array_keys($rootAttributes));
		return implode(' ', $qualifiedAttributes);
	}