I'm wondering if there are any logging frameworks available for XQuery? I've searched around and can't find much other than the built in fn:trace and fn:error functions. I'm looking for something that can log to different levels (e.g. INFO, DEBUG, ERROR) but also be disabled for no output. I was thinking it would be something built around fn:trace and fn:error.

I've considered writing a RESTful logging service – have others used this approach?