Yes, this is one of the half-assed, half-dead efforts I was referring to. Last commit Jan 2010, and even that one touched only some files, previous commits are all from 2008. It only supports a few languages - no C++, no Java, no .Net. The website itself says on the first page "relying on any implementation in production would be a bad idea". Plus, Rx doesn't offer the same functionality XML Schema does, from what I can find (only does type checking, no element order/count, default values etc).