Paper by Dongwon Lee and Wesley W. Chu comparing XML DTD, XML Schema, XDR, SOX, Schematron, and DSD...
Checks an XML document (specified by URL) for well-formedness and optionally DTD-based validity and...
Uses instance documents as a lightweight schema language; sample documents are marked up with the i...
Specification of a framework for modular validation of XML documents.
A open source multi-format schema converter based on RELAX NG. Includes documentation and download.