I'm wondering how to provide some degree of flexibility to the results provided by the service. I've been working about providing a possibility to color polygons.
As XML is quite a human-readable computer data format, I believe it is possible to make some changes like <description> and color code <color> elements. I don't think it's possible to edit geometries changing the XML text. It is necessary some GIS editor to modify geometries.
Probably I'll keep both XML and JSON file results when I have my own server. Although people prefer JSON for data interchange, I don't consider it human readable, that's why I want to provide both formats.
Update 28/05. After some attempts to edit clustering results, I noticed I was doing the same kind of editing in the first place, and been doing a few changes to the clustering process.