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

From: Pat Hayes <phayes@ihmc.us>
Date: Thu, 20 Sep 2007 15:12:28 -0500
Message-Id: <p0623091ac3187f7d5cf5@[10.100.0.19]>
To: Dan Connolly <connolly@w3.org>
Cc: Tim Berners-Lee <timbl@w3.org>, Technical Architecture Group WG <www-tag@w3.org>, Susie Stephens <susie.stephens@gmail.com>

>My main point is about numbers and numerals, near
>the end; I hope you'll read that far before you argue any of the
>lesser points...

OK, cut to chase here, other brief replies in another thread.

>>>If you have a proof that this is not so, I'm quite curious to see it.
>>
>>The proof I had in mind was the fact that just about any large 
>>first-order theory has nonstandard models, which follows from 
>>Goedel's theorem, for arithmetic,
>
>OK, yes, that's a proof, but it's a pretty obscure point; I wonder
>if it is really important for the purpose of this document, i.e. setting
>up web servers and such...

See below. I think that this document actually has a much wider range 
of application, even if y'all don't intend it that way. If all it was 
about was setting up web servers, I wouldn't even be reading the 
email thread. (And I know what you are thinking at this point, so 
don't say it.)

>>but informally (OK, its not a PROOF any more) is clearly true for 
>>almost any reasonably expressive theory with infinite models. Under 
>>these circumstances, no amount of ontological content or 
>>description is going to be enough to single out one sense of "Dan 
>>Connolly" from some others; and there will always be others. So 
>>apart from the above objection, and even if one buys into the 
>>fantasy of URIs being a globally unique naming system, there will 
>>still be SW issues that one ontology thinks of persons like you in 
>>one way and another ontology thinks of them in a different way. Im 
>>not sure how you like to describe this inevitable situation, but 
>>one way that makes semantic sense is to say that there are in fact 
>>two (and more) distinct entities, sorry resources, which are both 
>>'you'.  And its no defense to
>  > say that you FEEL like one thing. Of course we all feel like that: it
>>  only follows that this is what it feels like to be a whole lot of
>>  person-things at the same time.
>
>Yes, that point is well made, regarding formal systems.
>
>I suppose web server configuration files are, at some level,
>formal systems, but it seems to me that we gloss over the
>point about nonstandard models quite cost-effectively
>for lots of engineering purposes.

Oh, I agree.

>For typical engineering purposes, we agree what 1, 2, and 3
>identify, no?

Right.

>In a conversation with, say, a Java programmer,
>are you uncomfortable with saying that numerals identify numbers?
>If not, what would you say in that case?
>
>It seems to me that lots of programmers buy into the "fantasy"
>that numerals uniquely identify numbers, so the "one buys into
>the fantasy of  URIs being a globally unique naming system"
>situation isn't that much of a stretch, for the purpose
>of this "Cool URIs..." document.

Not for numbers, I agree. I'm not worried about the numbers. But this 
argument started when the TAG started talking about the SWeb and how 
URIs can, er, identify things simply by naming them.  Now, the SWeb 
tends to take numbers for granted just like everyone else: but for 
things like people and cars, its actually far less clear-cut. Im not 
making this next one up, now, it really is a hot-button point for 
actual deployed Web ontologies. Is a person a continuant and 
therefore not an occurrent? Or is the continuant/occurrent 
distinction meaningless (or maybe just not a strict taxonomic 
distinction)? DOLCE and BOF say the former, EPISTLE says the second 
(and I agree :-). So, now, consider two Web ontologies which mention 
people, one based on DOLCE and the other on EPISTLE. They both use 
your URI to refer to you. But what they each say about you is 
inconsistent with what the other says about you. Its not that they 
get any of the actual facts wrong, you understand: they just have 
different concepts of what a person is (and therefore, what you are.) 
And there's no evidence, no biological or social facts to appeal to, 
to decide that one of them is wrong and the other right. They just 
see the world through different-colored glasses. This isn't a fantasy 
or an ivory-tower niggle, the HCLS is running into this debate right 
now. So, what follows from this about that URI that names you? Is it 
really clear that it identifies one 'thing'? I agree that in the 
robust common-sense world it might do (though I still don't like the 
'identifies' language), but the SWeb isn't living in that commonsense 
robust world. All it has to go on is the ontologies we decide to give 
it, and they are going to provide multiple 'views' of our identified 
things, whether we like it or not.

Maybe its not the TAGs job to worry about such arcane topics. But I'd 
urge the TAG to accept that it should be at least aware of things 
like this, since these issues are already coming up in practice, and 
the TAG's pronouncements, when they actually do get finalized and 
emitted, do tend to be quoted with the authority of holy writ. Even a 
casual remark about URI's identifying cars and people can then be 
used to justify quite far-reaching decisions about SWeb semantics and 
(for example) how RDF should or should not be mapped into Topic Maps. 
So what the TAG says really does need to intersect rationally with 
such matters as ontological ambiguity. Sorry if this makes your job 
harder, but y'all did insist on calling it the WORLD WIDE web.

Pat

>
>--
>Dan Connolly, W3C http://www.w3.org/People/Connolly/


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Received on Thursday, 20 September 2007 20:13:09 UTC

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