The Java XML Validation API

See the original posting on IBM developerWorks – Java

Validation reports whether a document adheres to the rules specified by the
schema. Different parsers and tools support different schema languages such as DTDs, the
W3C XML Schema Language, RELAX NG, and Schematron. Java 5(TM) adds a uniform validation
Application Programming Interface (API) that can compare documents to schemas written in
these and other languages. Learn about this XML validation API.