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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 12:19:33 -0500
Message-Id: <p06230913c318555a7c78@[]>
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>

>Pat Hayes wrote:
>>>7. "On the Semantic Web, 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."
>>>Of course many people would consider the Traditional Web to 
>>>include mailto: links. Suggest:
>>>"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."
>>This seems to me to embody the central error which is causing so 
>>much trouble. In what sense can a URI (or indeed any name: the fact 
>>that is a URI is irrelevant in this case) be said to "identify" a 
>>real-world or nonexistent entity? The direct answer is, it CANT. To 
>>even use this word "identify" in this sense and in this kind of a 
>>case, is clearly and provably WRONG.
>It seems pretty clear that the name "Dan Connolly" identifies
>me and that I am a real-world entity.

You are real, I grant you. And "Dan Connolly" is your name. But does 
that name "identify" you? Seems to me that in order to justify this 
usage, it would have to be that if someone who didn't know you or 
anything about you were given just that name, "Dan Connolly", a 
string of 12 characters, that they could figure out from that string 
which real-world entity you actually are. Maybe not *locate* you, but 
at least single you out from all the the other DCs there might be. 
But in fact they couldn't, because there are others with the same 
name, who therefore it also 'identifies' if it identifies you. (Eg 

Is that enough of a proof?

Maybe this criterion is set too high, although I kind of transcribed 
it from the Web requirements for the "identifies" relationship 
between URIs and 'information resources'. But if this is too high, 
why do you and the TAG insist on saying "<name> identifies <thing>" 
instead of the more usual and completely non-puzzling "<name> is a 
name of <thing>" or even "<name> refers to <thing>" ? 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? We usually say "identifies" rather 
than merely "is a name of" when the identifier can be USED to single 
out the thing named from the universal multitude, just as an xxtp: 
URI can be USED to actually GET something. But names can't be used 
like this, in general: they are just names. They aren't anything like 
addresses or identifiers, because they don't identify. They just name.

>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, 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 


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

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Received on Thursday, 20 September 2007 17:19:44 UTC

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