Since WWW2007 I've been contemplating the Semantic Web vision as supported by various W3C activities, and I've also been thinking about the kind of programmatic Web that a fence-sitting MESTian/RESTafarian would like to see [*].
The thing is, they are not the same. Not by a long chalk.
While they both sit on the same physical Web, they are starting to look to me like very different overlays. The Semantic Web is (in theory) optimised for querying large amounts of vaguely structured data, using all kinds of fun things like RDF and OWL being developed by other fun things called committees and being standardised via a bunch of fun standards processes. All in all a great deal of fun to be had.
Although I can't really make this Web do anything for me, I can (in theory) ask lots of questions of it and it might be able to validate some assertions. Once all those fun activities have finished, of course.
The programmatic Web is a different beast altogether. It consists of resources whose representations I might or might not understand, and whose very formats (aka media types) I mightn't understand either. The links I might find embedded in any representations of those resources might be peppered with microformats which may also be meaningless to me, leading to other resources which may recursively baffle me in the same way.
But I am, oddly enough, optimistic about this Web's Babel because it is contextualised by the scope of the system I'm building to interact with it. My system (or service) may well understand some or all of the resource representations, links, and microformats that it will interact with because I will program it (preferably in a declarative manner) to understand those features. So it turns out that suddenly I can interact in a Web-friendly way with any resources that I know about or discover (hence the declarative bit). It doesn't need centralised agreement from a standards body or committee of experts, nor does it need to be transformed into "proper" Semantic Web via GRDDL or anything else from the Grand Data Web vision.
It just works the way it is, warts and all, in a localised context.
I find I like the programmatic Web much more than I like the Data Web. The programmatic Web shares the same key characteristic of the big Web, where innovation is decentralised and pushed to the edges of the network. Maybe it's not as big or grand as the Data Web vision, but at least it mostly works...
Flame on...
[*] The reason my head is in this space is because I'm firmly back into writing a book on the Web to compliment Leonard and Sam's fine effort, and my conference talks this year are all going to be Web-centric. But I still love message-orientation, just in case you're in any doubt.