I now have an object populated by categories and locations, and a page controller which shows the categories. Lots of work going into figuring out how to do what when; sequence is important when we're constructing lots of objects from asynchronous AJAX calls. Discovering differences between FF and Chrome which necessitate changes to the sequences. One emerging temptation is to pre-generate all the AJAX for the entire set of stuff and store it in eXist, then load it as a single object; that would be fastish, but possibly not responsive enough, in that you couldn't selectively load things that people have asked for. Next step is listing all the locations under their categories, then it's on to creating features on the map.