While noticing one of the scaling problems with Web services (a topic worthy of its own blog entry, but I can’t muster the energy), Dave Orchard suggests that XML’s “self-describing nature” will save the day.
Producing self-descriptive documents is hard. XML has some tools that help, in particular XML namespaces, and that it’s markup. But I see those as akin to having a hammer and nail in your hand as you attempt to build a house. XML’s “self-descriptive nature”, even if you accept that “XML” includes namespaces, is only slightly better than ASCII.
I’ve been doing a lot of self-describing data investigation over the past few weeks, and the last thing I consider important is which syntax is used. What I’ve found to be most important is that identifiers be URIs, and not to use an identifier where what it resolves to is what is really needed.