I just went and got James Clark’s new nXML Emacs XML editing mode. I poked around a bit, wondering which XML parser and RelaxNG engine he was using, and worrying how much trouble I’d have getting this running and hooked in to my hand-compiled Emacs here on OS X. No, it’s not like that. There are 12,587 lines of elisp here apparently implementing a complete XML 1.0 processor and RelaxNG validation engine. Words fail me.