Still very early days yet, but a tantelizing article at SearchWebServices.com suggests that the big boys are looking at Schematron. I’ll be interested to see how it pans out.
I see three drivers for Schematron
1) The human-centered diagnostic messages makes it an end-user
technology, not a guru technology like grammar-based validation.
2) The power to simplicity ratio of the technology, plus the cheapness of
implementation (open source built on mature existing technologies) gives
it the kind of bang-per-buck that is attractive to developers and good
for maintenance and familiarity.
3) Ultimately (are we moving into this stage now?) the need for vendors
to maximise their ROI as web services deployment turns out to be a hard sell.