A few people (this means you Trung!) have emailed me recently about more information in Schematron. Good news: Eric van der Vlist has just had a little PDFbook, in O’Reilly’s Shortcuts series, on Schematron
It appears to feature Gollum on the cover, according Christophe Lauret :-)
Eric gave me the chance to comment on a draft (I like to do technical editing on one or two books a year, to keep my hand in), so I will be interested to see how it shaped up. I think Eric tackles pretty well that we are currently on a cusp, with some people using Schematron 1.5 and some moving on to ISO Schematron.