Retrieve Elements of the current Service node by their name, and return
as a SimpleXMLElement object. The Elements should be direct children of the Service node. This method basically just passes the $element string as an XPath query so it's open to other uses despite the assumed use case.
Return an array of Service Type URI strings. This method will NOT validate the resulting URIs. URI values in the array will have key values matching their priority, and be ordered based on their priority values - highest (i.e. lowest integer) priority first.