To expand on Eve's suggestion, we should develop a standard list of XML parsers (and other tools) that guide our conformance testing for guidelines. Here is a start: Xerces-J Xerces-C++ Apache Crimson (does this support XSD?) Tibco Extensibility XML Spy W3C XSV IBM XML Schema Checker (on alphaworks) The last two are often suggested as the most conformant with the spec.