When I first started speaking to audiences on the NFJS tour a few years back, I presented on RELAX NG — the world’s only comprehensive and sane XML schema language. At the time, I spoke to audiences that nearly universally had never heard of it and some subset of whom either quietly or rather vocally considered me stupid, crazed, or simply naive for considering it a viable option.
I admit, back at the height of XML Schema‘s popularity, I was perhaps tilting a bit at the windmills. Don Box told me in a group setting essentially, “If I could wave a magic wand and make us all use RELAX NG, I would, but XML Schema won. Get over it.”
(My old RELAX NG slidedeck is here; I think this dates back to 2004).