- From: Williams, Stuart <skw@hplb.hpl.hp.com>
- Date: Fri, 20 Sep 2002 15:22:04 +0100
- To: "'Tim Bray'" <tbray@textuality.com>
- Cc: www-tag@w3.org, Norman Walsh <Norman.Walsh@sun.com>
Hi Tim, > -----Original Message----- > From: Tim Bray [mailto:tbray@textuality.com] > Sent: 19 September 2002 17:15 > To: Norman Walsh > Cc: www-tag@w3.org > Subject: Re: My action item on Moby Dec, issue 14, etc > > > > Norman Walsh wrote: > > > The error, I think, is that you've brought representations into the > > picture. The important part about "Absolute URI references are > > unambiguous: Each absolute URI reference unambiguously identifies one > > resource." isn't the consistency of the representations you can > > dereference, it's the fact that they're fully qualified and globally > > unique. That's why we can paint them on billboards, write them on > > busses, and flash them in commercials. > > OK, I think that what you're saying is that a resource is simply that > which is identified by a URI. I agree with this and think it's > consistent with the 2396 definition too. Given this, our "principle" is > a tautology and not in the slightest worth saying. Hmmm... I think your shifting the ground. That "a resource is simply that which is identified by a URI." may be a tautology, but the prinicple Norm quoted was "Absolute URI references are unambiguous: Each absolute URI reference unambiguously identifies one resource." which I think is worth articulating as a principle of Web Architecture (if it is a principle that 'sticks'). > Spin it another way: the URI, and the representations you can (maybe) > get with it, are all there is. Sure... a resource is experienced through the representations exchanged with it and what other resources ['meta-data resources'] have to 'say' about it. If you are not interested in the what these other resources have to say, then the URI and representations exchanged with a given resource is indeed all you have. > There is no point in arguing about the fundamental nature of what the URI identifies and what the > representations represent, Agreed. I've got to this point by concluding that TimBL's expression of the issue, that HTTP URI (no fragment) must not/should not be used it identify abstract concepts or non networked real-world artifacts (people, cars, mountains, whales...) is secondary to a concern ambiguity in the use of URI (HTTP URI). > because (a) you can never know, and Yes, from the point of view of experiencing a resource through exchanges of representations with that resource, and from the point of view that the resource itself and others can lie or disagree about the nature of a given resource. The URI assignment may authoratively assert the nature of a resource, but I guess a resource is in the eye of the beholder... and what they choose to believe it to be may be influenced by others, but fundementally is under their own control. > (b) it > doesn't matter. What matters (I think) is being able to tell that assertions, made at different times and by different entities, are being made about the same thing - even if those assertions are contractictory. It does matter that at least within some context of use (spatial, temporal... possibly universal) a given identifier or reference identifies or refers to the same thing. > Furthermore, in the context of using URIs to build KR systems a la RDF, > the notion that you can banish ambiguity by architectural fiat is simply > wrong and dangerous to the future of the semantic web. -Tim Hmmm... can you un-pick this a bit. Can you expand on "dangerous"? It seems to me that the 'intended' universal absense of ambiguity in the relationship between an identifier and a resource was part of the original design of the Web. Cheers, Stuart
Received on Friday, 20 September 2002 10:22:21 UTC