Is it possible to add selection controls? Instead of using, for example
radiobuttons, to evaluate a service, I would like to use stars so that the
user can evaluate a particular service. Is it possible to do in Orbeon?
Yes, this is possible. You would do this using XBL. If you'd like to give it
a go, there is some doc about it (see 1st link below), and you can also look
at the source of existing XBL components that ship with Orbeon Forms. This
being said, XBL can be tricky, so, yes, go through the doc, read the
examples, but also don't hesitate to ask questions here if something doesn't
seem to make sense to you.