I’ve been paying attention to “building blocks of XML” as a mechanism of standardizing dataformats for a while. XML certainly is the tool which is supposed to be able to solve this. And in a few isolated spots it has worked. But for the most part, applications still don’t share a lot of data types for a lot of reasons.
A group called StructuredBlogging has some interesting ideas around doing this within blog. They have an interesting demo for MovableType or WordPress. They are also supporting the notion of Microformats.
Its a bit of kludge, though, because it is shoehorning in XML data types into HTML which wasn’t really intended for it. It makes the syntax a bit obscure, and you lose namespaces and need to be a lot more careful about what XHTML class attributes you use. But, if it gets past the adoption problems of XML, those are minor issues.
Worth reading about if you are interested in this kind of stuff…. I do wonder if the real issue is that too many businesses think they don’t want to share data types at all… (Look what happened with Oodle/Craigslist when they shared data via RSS) I hope that is not really the case.
Finally, if you are interested in this, definitely read what Tim Bray has to say about inventing XML languages.