In case there are other users of XQuery who are looking for a way to get an XQuery engine on the Web but are not sure how to go about it, I have described my adventures setting up one approach (running BaseX 7.9 under Tomcat 6 on a commercial Java hosting provider) in a blog post today, hoping that it might enable someone else to do it with less trouble and confusion than I had:
When time allows, I expect to upgrade my Tomcat to Tomcat 7 so that I can install a current BaseX; I'll update the post then with information for BaseX 8.*.
if those who understand Java development and deployment better than I do (or wish to do) find errors in the exposition or simpler ways to get things set up, I would be glad to have them pointed out.
I'd also be interested in speculations as to why setting the default user in web.xml seems not to have worked, but at this point I doubt that it's worth significant effort to solve that problem.