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Re: Terminology Question concerning Web Architecture and Linked Data

From: Chris Bizer <chris@bizer.de>
Date: Sun, 22 Jul 2007 15:25:36 +0200
Message-ID: <006101c7cc63$ca248c90$c4e84d57@named4gc1asnuj>
To: "Mark Baker" <distobj@acm.org>
Cc: <www-tag@w3.org>, <semantic-web@w3.org>, "Linking Open Data" <linking-open-data@simile.mit.edu>

Hi Mark,

interesting point of view.

> [...]
>> Question 1: According to the terminology of the Architecture of the WWW
>> document [4] are all these URIs aliases for the same non-information
>> resource (our current view) or are they referring to different resources?
>> Does the TAG finding "On Linking Alternative Representations To Enable
>> Discovery And Publishing " [5] about generic and specific resources apply
>> here, meaning that the URIs 1,2,3,5 refer to different specific
>> non-information resources that are related to one generic non-information
>> resource?
> IMO, those URIs identify different resources.  I say this because they
> all return different representations when I dereference them.  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.

But I think I prefer to follow Dan's view on this 
(http://lists.w3.org/Archives/Public/semantic-web/2007Jul/0102.html), as by 
seeing them as URI aliases you get a nice straight architecute that 
harmonizes with 303 redirects, content negotiation and alike.

As you said, if they were different resources you run into problems with 
agency. Seeing them as URI aliases solves these problems as we tried to 
explain in our Linked Data tutorial 

"Within an open environment like the Web it often happens that multiple 
information providers talk about the same non-information resource, for 
instance a geographic location or a famous person. As they do not know about 
each other, they introduce different URIs for identifying the same 
real-world object. For instance: DBpedia a data source providing information 
that has been extracted from Wikipedia uses the URI 
http://dbpedia.org/resource/Berlin to identify Berlin. Geonames is a data 
source providing information about millions of geographic locations uses the 
URI http://sws.geonames.org/2950159 to identify Berlin. As both URIs refer 
to the same non-information resource, they are called URI aliases. URI 
aliases are common on the Web of Data, as it can not realistically be 
expected that all information providers agree on the same URIs to identify a 
non-information resources. URI aliases provide an important social function 
to the Web of Data as they are dereferenced to different descriptions of the 
same non-information resource and thus allow different views and opinions to 
be expressed. In order to still be able to track that different information 
providers speak about the same non-information resource, it is common 
practice that information providers set owl:sameAs links to URI aliases they 
know about. This practice is explained in Section 5 in more detail."



>> 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 13:25:55 UTC

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