Since arriving at the party in 2001, RELAX NG, a nifty schema language for XML, has grown from an OASIS committee spec into an international standard (ISO/IEC FDIS 19757-2:2002). Some shrug it off in favor of the more widespread XML Schema, but those who are well aquainted with RELAX NG find it hard to shrug it off, least of all on technical grounds. As John Cowan once put it, “Once RELAX NG’s concepts have crossed the blood-brain barrier, you will never be able to take any other schema language seriously again.”
That’s why I am glad to see RELAX NG getting attention at the W3C. I mean, they invented XML Schema, so why would they bother with a competitor? Well, that’s because RELAX NG is hard for the astute mind to resist. Right now at the W3C, the current working draft of XHTML 2.0 is sporting a RELAX NG schema. You can also find a RELAX NG schema (in compact syntax) in the RDF/XML syntax spec, in WSDL 2.0, SVG 1.2, and unofficially for XML Signature.
I think we have advocates like Masayasu Ishikawa and others at the W3C, including Chris Lilley, Dean Jackson, and Joseph Reagle, to thank for the the RELAX NG incursion into W3C. You just can’t keep a good schema language down.
Do you use RELAX NG? Let’s hear why or why not.