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Re: Some TAG review of "Cool URIs for the Semantic Web"

From: Dan Connolly <connolly@w3.org>
Date: Mon, 24 Sep 2007 16:21:49 -0500
To: Pat Hayes <phayes@ihmc.us>
Cc: Tim Berners-Lee <timbl@w3.org>, Technical Architecture Group WG <www-tag@w3.org>, Susie Stephens <susie.stephens@gmail.com>
Message-Id: <1190668909.12486.132.camel@pav>

On Thu, 2007-09-20 at 15:59 -0500, Pat Hayes wrote:
> >>Isn't this 'identifies' usage supposed to suggest SOME kind of 
> >>similarity between the URI-to-information-resource relationship and 
> >>the URI-to-Dan Connolly relationship?
> >
> >Yes, of course.
> Well, you can say that the first one is a (very) special case of the 
> second, with the Web added, I guess. But even that isn't obvious: its 
> only true by stipulation.

I can go with that. "true by stipulation". I'd say that's the
nature of must/most of Web Architecture. It's true by stipulation...
or perhaps: it's a way of looking at things.

It seems to me that these 3 situations are completely analogous:

A: 1, 2, and 3 identify numbers
B: http://xmlns.com/foaf/0.1/Person identifies the class of persons
C: http://www.w3.org/2002/07/owl#Class identifies the class of classes

In the case of numerals, you're happy to stipulate that they
identify numbers even though we both know that there are
multiple theories about how to construct numbers out of sets,
and they're mutually inconsistent.
( http://en.wikipedia.org/wiki/Natural_number gives details.)
And we know that this is not a bug to be fixed, but a fact
about sufficiently rich formal systems.

Likewise, for social networking purposes, the FOAF community
stipulates that foaf:Person is that class of things with
roughly 6 billion bipeds in it, largely oblivious
to the DOLCE and EPISTLE refinements of this way of thinking.

And for lots of purposes, http://www.w3.org/2002/07/owl#Class
is the class of things that stand in the rdf:type relation
to something (plus the owl:Nothing class), and it doesn't
matter whether you look at it from the OWL DL or the OWL Full
formal definition. Yes, the WebOnt WG gave two definitions
for this resource, and the rest of W3C went along with it.
I think this is somewhat counter to "URIs Identify a Single Resource"
http://www.w3.org/TR/webarch/#pr-uri-collision but the
cost of being architecturally pure might have been even higher,
and we all seem to get along. At least the two definitions
don't conflict in any way that's observable within the formalisms.

It's in that sense that I think the TAG is reasonable in
suggesting this text for the "Cool URIs..." document:

"On the Semantic Web, http: URIs identify not just Web documents, but  
also real-world objects like people and cars, and even abstract ideas  
and non-existing things like a mythical unicorn. We call all these  
things resources."

[... though I'm somewhat persuaded to take unicorns out of there.]

Now you could continue this argument and say
that there are similarly two conflicting
theories about http://www.ihmc.us/users/phayes/PatHayes , one
that says it's a web page and one that says it's a person, but
for many purposes, there's no need to look at things that closely.
The TAG decision on httpRange-14 is that if you look at
things closely enough to get a 200 response, then it's an
information resource, and hence not a person. I continue to
think that's good advice, though I'm fully aware that it's
not the only coherent rational position to take.

> No, that "identify" is one case of "name". Which is true enough for 
> government work, I will agree. But not all names are identifiers, is 
> my point.

On that and other matters, I'll perhaps reply separately.
I'm still thinking it over.

Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Monday, 24 September 2007 21:22:15 UTC

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