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Re: removing constraints on 'resource' [024-identity]

From: Pat Hayes <phayes@ihmc.us>
Date: Tue, 15 Jun 2004 11:13:04 -0500
Message-Id: <p06001f1ebcf4c88a783f@[]>
To: Martin Duerst <duerst@w3.org>
Cc: Dan Connolly <connolly@w3.org>, Stuart Williams <skw@hp.com>, uri@w3.org, Tim Bray <tbray@textuality.com>, Joshua Allen <joshuaa@microsoft.com>, msabin@milessabin.com

>Hello everybody,
>I'm writing this mail in the hope that we can move forward on this
>and finally complete the work on the URI spec update.
>(even if I know that I risk to stir things up a bit)
>At 16:01 04/05/27 -0500, Pat Hayes wrote:
>>>On May 27, 2004, at 11:02, Pat Hayes wrote:
>>>>BTW, the diagram cited below (Im looking at the one at 
>>>>http://www.w3.org/DesignIssues/diagrams/URI-space.png ) directly 
>>>>embodies that confusion/ambiguity very clearly. There are two 
>>>>black arrows at the bottom, one going from 'hypertext' to 
>>>>'anchor', the other going from 'semantic Web' to 'anything'. 
>>>>The first refers to identification on a network, and belongs in 
>>>>my "C' category: the second arrow is denotation, which has 
>>>>nothing to do with computation and belongs entirely in the D 
>>>Yes.  The first is hypertext architecture; the second is semantic 
>>>web architecture.
>>Well, its actually SWeb semantics. Im not sure that semantics and 
>>architecture are the same kind of thing.
>>>  They are different.
>>>A warning: read the diagram carefully: it is not a venn diagram of 
>>>resources, but of URIs.
>>>Sets -- subset of URIs -- are labeled in roman text, or typewriter 
>>>text with syntactic constraints such as URI scheme.  Then, some 
>>>regions in the diagram are annotated in italic with some examples 
>>>of the things which can be *identified by* those URIs.
>>Ah. Ok, then my point is better stated thus: there are two 
>>different senses of 'identify' being used here. The sense in which 
>>an XHTML URI+localId "identifies" an anchor is not the same as that 
>>in which an RDF URI+localId "identifies" whatever it denotes.  One 
>>single URI+localID could identify an anchor in one sense and also 
>>refer to something completely different in the second (SWeb) sense. 
>>The two relationships of 'identification' have nothing particular 
>>to do with one another, a priori.
>Yes. So this seems to look like an important distinction that should
>carefully be reflected in the draft. But after further thinking, I got
>to a different conclusion:
>The basic idea of URIs is that they allow to use a single space of
>'identifiers' to be used for all kinds of things, systems, operations,
>concepts, what not. This has huge advantages, because it can produce
>huge synergies and network effects.

Right, no contest. Im not arguing against having a single space of 
identifier-thingies. Im just asking that we be a little clearer about 
two rather different senses in which they can be said to identify 
(because things that are sensible, useful and worth saying about one 
sense are flat wrong for the other one).

>It also has clear limitations,
>not everthing works with everything
>(ever used a mailto: URI in an html:img src attribute?).
>The Web and the Semantic Web are clearly very important uses
>for URIs. But should they, or will they, be the only uses?

Well, maybe not, although I have to say that covering the Web and the 
Semantic Web is enough coverage for me, and certainly all the 
coverage that I would expect the W3C to be making authoritative 
pronouncements about. Do your ambitions really go wider than this? 
Can you sketch the limits of your vision, if only roughly? (Do you 
see URIs as being the basis of a new Esperanto which will replace all 
the world's languages?)

>I hope not. So I think that rather than making distinctions
>that we can agree are very important for some usages of URIs,
>I think we should try to stay as general as possible.

Sigh. Im not asking that we be less general. Im only asking that the 
wording be clear. Saying 'there are two kinds A and B, and A's are 
foo and B's are baz' is not being less general, its being clearer. 
It is VERY hard to find words which cover ALL ways of using URIs 
without accidentally confusing the issue for SOME ways of using them. 
For example, the idea that URIs identify, itself - that is, that 
there is a particular, SINGLE, resource identified by each URI - is 
wrong for some potential uses: its already wrong for the Semantic 
Web, in fact.  The idea that resources are time-dependent functions 
yielding representations (welded into the foundations of the REST 
architecture which is explicitly referenced by RFC 2396) is wrong for 
the Semantic Web, in fact its wrong almost everywhere except the 
classical Web itself. And so on.

Making clear statements about very, very general matters is doing 
philosophy.  Philosophy is very tricky stuff to get right.  I don't 
recommend that the architecture document tries to do philosophy; but 
if it must, then I recommend that the W3C hires some competent 


>Regards,    Martin.

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Received on Tuesday, 15 June 2004 12:12:54 UTC

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