This week's book giveaway is in the OCMJEA forum. We're giving away four copies of OCM Java EE 6 Enterprise Architect Exam Guide and have Paul Allen & Joseph Bambara on-line! See this thread for details.
Well, seems to me the first thing you would need would be a Schematron implementation written in Java. The Schematron site provides links to somebody who has written one. Following those links might also lead to information about how to use said implementation.
My Google keywords were "schematron java" by the way.