So Apple support "podcasting" ie. RSS + enclosures in the new iTunes. Everyone expected, and welcomed, it. But now we find they're defining their own extensions. As are Microsoft, Yahoo etc these days.

Comments from
Danny Ayers, Dare Obasanjo, Dave Winer etc.

I think this is going to be a great acid test of the two "semantic web" or "interop" philosophies that I was talking about a few weeks ago.

The SemWeb people, or at least Danny, are clearly laughing their socks off sceptical. What chaos will ensue, as writers of clients for feeds based on these extensions will have to learn them all.

It is a good empirical test. If the SemWeb people are right, the spiralling cost of incompatibility between different extended brands of RSS will kill podcasting and syndication with enclosures. Or at least will kill the RSS 2.0 branch of it. And either the world will devolve into incompatible walled gardens or suppliers and consumers will have to renegotiate around Atom or other RDF based format.

If the alternative theory is correct ie. that semantics are best thought of as being determined by the document-context, (and assuming podcasting is worth having at all), then the aggregator players are just going to bite the bullet and pay the cost of learning each of the major suppliers' extensions. And this, in practice, won't turn out to be too difficult. All the information as to how to interpret Apple's new tags is easily available, it's all framed within the context of consuming a podcast feed, so if you know what podcasting is and is for, then you know what you'll need to do.

(Aside : If Apple's iTunes:owner means exactly the same thing as DC:publisher, then the consuming program can simply use the same subroutine to handle both of them. It's just another branch of a case statement somewhere ( ;-) ) And if it doesn't mean exactly the same thing, then re-using an existing element type is harmful rather than helpful.)

Incompatible HTMLs and browsers made life hell for web-creators, but they didn't kill the web. It was too useful for that. If these extensions are worth having, customers will want them, and aggregator writers will pay the price of finding out about them. That's the golden rule of markets, until there's cut-throat competition between suppliers, the consumer pays for delivery. (Of course, on the web, the producers paid the cost of compatibility with the browsers, but that was because there were a lot more sites than browsers.)

Danny, rightfully, sneers at the <itunes:explicit> tag. But I understand Apple's frustration. When I tried to learn RDF a couple of years ago, the first problem I ran into was how to represent boolean values using it. No-one ever gave me a simple and satisfactory answer.

Finally, I'm not so clear what Apple should have done if they'd wanted to add their itunes:explicit tag to say, RSS 1.0 or Atom. Wouldn't they have still had to define a an iTunesCore ontology for it, which aggregator writers would have had to learn about in order to do something useful with?