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Re: Terminology Question concerning Web Architecture and Linked Data

From: Richard Cyganiak <richard@cyganiak.de>
Date: Sun, 22 Jul 2007 17:38:52 +0200
Message-Id: <C3AA36DE-4B1D-4251-B14F-A9595421A917@cyganiak.de>
Cc: "Chris Bizer" <chris@bizer.de>, www-tag@w3.org, semantic-web@w3.org, "Linking Open Data" <linking-open-data@simile.mit.edu>
To: "Mark Baker" <distobj@acm.org>


On 22 Jul 2007, at 14:37, Mark Baker wrote:
> On 7/7/07, Chris Bizer <chris@bizer.de> wrote:
>> 1. DBpedia: http://dbpedia.org/resource/Tim_Berners-Lee
>> 2. Hannover DBLP Server:
>> http://dblp.l3s.de/d2r/resource/authors/Tim_Berners-Lee
>> 3. Berlin DBLP Server:
>> http://www4.wiwiss.fu-berlin.de/dblp/resource/person/100007
>> 4. RDF Book Mashup:
>> http://www4.wiwiss.fu-berlin.de/bookmashup/persons/Tim+Berners-Lee

[...]

> IMO, those URIs identify different resources.  I say this because they
> all return different representations when I dereference them.

You forget that there's a 303 redirect in each of these cases. In  
other words, the representations you see are representations of  
*other*, related, information resources. They are *not*  
representations of the resources identified by those URIs.

Quote Roy's proposed new description for 303 See Other [1]:

| A 303 response to a GET request indicates that the requested resource
| does not have a representation of its own that can be transferred by
| the server over HTTP. The Location URI indicates a resource that is
| descriptive of the requested resource such that the follow-on
| representation may be useful without implying that that it adequately
| represents the previously requested resource. Note that answers to the
| questions of what can be represented, what representations are  
adequate,
| and what might be a useful description are outside the scope of  
HTTP and
| thus entirely determined by the resource owner(s).

In other words: We don't know if the resources above have any  
representations. Thus, your conclusion that they must be different  
resources is unfounded.

Yours,
Richard

[1] http://www.w3.org/Protocols/HTTP/1.1/rfc2616bis/issues/#i70



>   If they
> identified the same resource then their representations would be
> identical (see Roy's definition of resource in his REST dissertation).
>
> The tricky bit here is to remember to account for agency; to recognize
> that although dbpedia.org uses URI #1 to identify Tim, from a third
> party's POV it identifies dbpedia.org's *view* of Tim.
>
>> Question 3: Depending on the answer to question 1, is it correct  
>> to use
>> owl:sameAs [6] to state that http://www.w3.org/People/Berners-Lee/ 
>> card#i and
>> http://dbpedia.org/resource/Tim_Berners-Lee refer to the same  
>> thing as it is
>> done in Tim's profile.
>
> No.  AIUI, owl:sameAs is a very strong predicate which declares
> subject and object to be the same resource.  I only foresee it being
> used by a publisher to declare equivalence of their own URIs, because
> being able to guarantee equivalence requires a very tight degree of
> control over them (i.e. be able to serve identical representations for
> all time).
>
> Mark.
> -- 
> Mark Baker.  Ottawa, Ontario, CANADA.         http://www.markbaker.ca
> Coactus; Web-inspired integration strategies  http://www.coactus.com
>
>
Received on Sunday, 22 July 2007 15:39:10 GMT

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