W3C home > Mailing lists > Public > semantic-web@w3.org > June 2007

Re: owl:sameAs use/misuse/abuse Re: homonym URIs

From: John Black <JohnBlack@kashori.com>
Date: Fri, 15 Jun 2007 10:09:25 -0400
Message-ID: <1e6a01c7af56$c86f15c0$6601a8c0@KASHORI001>
To: "Bernard Vatant" <bernard.vatant@mondeca.com>, "Tim Berners-Lee" <timbl@w3.org>
Cc: <semantic-web@w3.org>

Bernard Vatant wrote:
>
> Tim Berners-Lee a écrit :
>>> Although I agree with Pat below (see my previous message) suppose I (or 
>>> Richard) disagree(s) and want(s) to stick to the assertion
>>> http://dbpedia.org/resource/Berlin owl:sameAs 
>>> http://sws.geonames.org/2950159/
>>>
>>> Does that mean that what I get from the two resources should be not only 
>>> consistent RDF descriptions, but *identical descriptions* ?
>>
>> Absolutely not.   The URIS above stand for the same thing, but the 
>> documents you get when you look them up (via 303 to 
>> http://sws.geonames.org/2950159/about.rdf etc)  have different URIs 
>> different from those of the city.
> Indeed, that's exactly my point
>>
>> Different documents about the same thing is of course an essential 
>> element of the world.
> I understand that also. But is not 'A owl:sameAs B' intended to mean, by 
> OWL definition, that in any context using the semantics of URIs, those 
> semantics are the same for A and B, so whatever assertion is true of  A is 
> true of B, so A and B can be used indifferently. But if through http 
> protocol  you retrieve "what the owner of A declares is true of A" and 
> "what the owner of B declares is true of B" (read : RDF descriptions of A 
> and B), with no certitude whatsoever if those descriptions are consistent 
> or not, that means http protocol is not a context where A and B have the 
> same semantics.

Or does it just mean that the owl:sameAs is sometimes false? Sometimes the 
individual denoted by A is not, in fact, the same as the individual denoted 
by B. Or else A and B do denote the same individual and either some 
assertion in the description of A is false or some assertion in the 
description of B is false.

>
> I can live with that, but it seems at least hard to understand and harder 
> to explain, if one judge by the everthread about it.
> OTOH, if one uses owl:sameAs for URIs identifying resources which are 
> *information resources*, then they should actually redirect to the same 
> document. Yes?
>

That sounds logical, but the HTTP/RDF/OWL lawyers know best.

Here is a related question, stated informally:

Is it a part of the web / semweb architecture that:

for all URI it is   owl:sameAs    the graph of the RDF/OWL downloaded via 
HTTP using that URI

provided the HTTP path includes a 303 redirect

and

for all URI it is   owl:sameAs    the bits downloaded via HTTP using that 
URI

provided an HTTP get returns 200 ok?

John

>
> -- 
>
> *Bernard Vatant
> *Knowledge Engineering
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Received on Friday, 15 June 2007 14:10:01 UTC

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