The new architecture was being created for the workers. The holiest of all goals: perfect worker housing. - Tom Wolfe The thread that wouldn't die. Tim Bray disagrees with Mark Pilgrim around URIs as identifiers. Let's summarize. Marks' position, which is fairly specific to Atom: Permalinks are transient, not permanent. Keep permalinks and ids distinct. Prefer tag: URI constructs for ids. Tim's position, which strays beyond Atom: Get decent software that generates context free URIs. Permanently own a domain. Don't use tag: URIs because they're not registered (but don't think hard about why that is). Anything else is web-unfriendly (specifically you'll burn bookmarks, Pagerank and caches) Tim's position is on the face of things, very sensible, and is essentially core W3C dogma - cool URIs don't change. But Tim's left out some details that happens to strengthen Mark's position and derail his. In short - forget about the application software; the Web/Internet infrastructure doesn't support cool URIs. Never mind the URI. Tim: If you think that theres a good chance your URIs will change, you shouldnt use them for IDs. But, if you think that, you should also bloody well be looking for better software or hosting or whatever. Let's talk about ICANN instead. We can bang on all day about getting tooled up with decent software to generate sensible URIs and not harm Pagerank (please...), but that is to neglect issues around domain name ownership, which cannot be solved in software. The dirty secret of the Web is that you don't own your domain name; you rent it. As soon as you stop renting it, every URI under that namespace is almost certainly toast, irrespective of whether someone else rents it after you. What kind of permanence is that? No-one will support your ex-URI space because it cost money to serve up content on the web and the more read you are (or were) the more it costs. No amount of non-broken software will not help you here - but an id tag will. But, having said all that, here's my (strawman) counter-argument : If you think that theres a good chance your URIs will change, you shouldnt use them for IDs. But, if you think that, you should also bloody well be looking for better domain name governance or perpetual rights to domain names or a more democratic web or a web that doesn't punish content providers or whatever. Arguing for permanance in http: URIs when the critical partition of the http: namespace, the domain, is de facto transient - make what you will of it. Web Realpolitik. I dislike Mark Pilgrim's position, because it involves managing the relationships between various identifiers, which can get complicated (and is prone to inconsistencies). It is also not general purpose whereas using a lone URI is. I think it helps to have to had to manage names like this and integrated two or more systems with localized name spaces to appreciate what a compelling idea the lone URI is. Consequently the Atom id tag sucks. Unfortunately Mark's position does address issues with URI transience. Consequently the Atom id tag sucks, and I will be using it. Emotionally, I like where Tim's coming from better, but emotionally I like world peace better too. Short of radically different web infrastructure and management, Mark's way works will work out better for most folks. "Cool URIs don't change" doesn't work so well unless you are in position to guarantee perpeptuity. For me that means roughly 150 euros a year (well worth it) and nobody trading on the name "dehora" coming to root me out of that domain (we'll see about that being worth it). I don't know - the cool URI view seems to belong in a advertisement by Carlsberg, who don't do web architecture, but if they did it'd probably be the best web architecture in the world: power is decentralized to the edge peers, people own their domain names, they can affordably serve content, they can host their own content, they can continue to do so when the world loves to read their content, they can avail of sensibly crafted software so they don't have to be programmers if they don't want to be, they don't get hounded out the domains they have, bodies like ICANN and the IETF are running like well-oiled machines, and the physical architecture supports what the web architects want. The web we have is not like this - it is natted, centralized, dynamically assigned, firewalled, attacked, mismanaged in part, inefficient, litigated over, awash in expediency, filth, greed and infection. The Web is much more like the real world than the Web. Or perhaps Rome got sacked and we're living in the Web's Dark Ages. Death and taxes. The deployed Web works against cool URIs not for them. That's what Mark Pilgrim understands and the W3C does not. To have cool URIs under your namespace is to actively fight against entropy. Mark: 'Permalink changes'? Yes, permalinks are not as permanent as you might think. Heres an example that happened to me. My permalink URLs were automatically generated from the title of my entry, but then I updated an entry and changed the title. Guess what, the permanent link just changed! If youre clever, you can use an HTTP redirect to redirect visitors from the old permalink to the new one (and I did). But you cant redirect an ID. I don't have a problem using titles in Atom permalinks, or with using tag: URIs in Atom ids. I've come to decide that I won't change titles post publication. As for tag: URIs - I happen to be a fan of these. Despite whatever problems Tim has reading them, I find them easy enough to eyeball. It takes 15 minutes to implement a generator. The fact the scheme is not registered doesn't matter because the reason it's not is not a technical/engineering matter; it's down to an obtuse registration process. Again this is an issue that goes beyond software and comes down to management. So I say go ahead and use tag: URIs. Despite all that I'm up for following Tim's line; I will continue dole out per annum to rent and host dehora.net for as long as I can afford it. I am careful about issuing permanent URIs, but definitely not careful enough - for example I recently had to port most of the URIs for this blog leaving behind redirects as Mark describes above. I just happen to think it's unrealistic to expect more than a small minority to do likewise; there are other things to be doing that agonizing over URIs and the lifespan of a domain name. [limp bizkit: faith]...
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