We are developing an application that involves a substantial amount of XML transformations. We do not have any proper input test data per se, only DTD or XSD files. We\'d li
I think Oxygen (http://www.oxygenxml.com/) does it as well, but that's another commerical product. It's a nice one, though... I'd strongly recommend it for anyone doing a lot of XML work. It comes in a nice Eclipse plugin, too.
I do believe there is a free, fully-featured 30 day trial.