jing is an XML validator implemented in Java. It validates against the
RELAX NG schema language and implements the following features:

* RELAX NG 1.0 Specification

* RELAX NG Compact Syntax

* Parts of RELAX NG DTD Compatibility (checking of ID/IDREF/IDREFS)

It also comes with experimental support for schema languages other than
RELAX NG:

* W3C XML Schema (based on Xerces-J)

* Schematron

* Name Space Routing Language