I have a php function that returns an xml output I would use to populate a map with. I know how to do it in Objective C but I am left clueless about how to asynchronously execute operations with the date received from a url response in javascript.
The url is:

and I would like to use the latitudes and longitudes in the response to populate a map by means of the following code:

var marker = new GMarker(new GLatLng(<Latitude>, <longitude>));
Thanks for your help,