Generating sample XML Document from their DTD or XSD?

We are developing an application that involves a substantial amount of XML transformations. We do not have any proper input test data, only DTD or XSD files. We’d like to generate our test data ourselves from these files. Is there an easy way to do that?

Oxygen ([]( does it as well, but that's another commerical product. It's a nice one,It comes in a nice Eclipse plugin, too.