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Re: owl:sameAs - Is it used in a right way?

From: David Booth <david@dbooth.org>
Date: Sun, 17 Mar 2013 21:40:33 -0400
Message-ID: <51467091.3050806@dbooth.org>
To: Jim McCusker <mccusj@rpi.edu>
CC: Alan Ruttenberg <alanruttenberg@gmail.com>, Erich Gombocz <egombocz@io-informatics.com>, Jeremy J Carroll <jjc@syapse.com>, Umutcan ŞİMŞEK <s.umutcan@gmail.com>, Kingsley Idehen <kidehen@openlinksw.com>, w3c semweb HCLS <public-semweb-lifesci@w3.org>
 > On Sun, Mar 17, 2013 at 12:51 AM, Alan Ruttenberg wrote:
 >
 >     My dad's name is Danny. I've known him a Long time, during which
 >     he's changed a lot. Am I supposed to stop calling him dad because
 >     he's not precisely the same as he was when I was 10?

On 03/17/2013 01:05 AM, Jim McCusker wrote:
> No, that symbol contains the full scope over which you've known your
> dad, plus anything you've learned about him before. However, there are
> narrower contextual scopes in which you may make specific claims about
> that may not always be true (my Dad when I was 12, for instance).

Exactly.  In one contextual scope certain properties of :alansDad hold 
-- that's the notion of :alansDad over his whole life -- and in a 
narrower contextual scope certain *additional* properties of :alansDad 
hold, such as the fact that he is 12 years old.

In the semantic web world, these "contextual scopes" are RDF graphs.

Now we can see that in a different "narrower contextual scope" (i.e., a 
different RDF graph), someone might make statements about :alansDad when 
he was 26.   Suddenly, this graph is inconsistent with the graph that 
asserted that :alansDad was 12.  This is exactly the problem illustrated 
in Figure 26:
http://dbooth.org/2010/ambiguity/paper.html#inconsistent-merge

A different URI could be used for Alan's dad in each of these "narrower 
contextual scopes" (i.e., different graphs), such as :alansDadAt12 and 
:alansDadAt26.  The downside of this is that if different URIs are used, 
it is much harder to know that they are all talking about the same thing 
. . .  well, the same thing at one granularity (:alansDad), but 
different things at a finer granularity (:alansDadAt12 and 
:alansDadAt26).  This problem can be mitigated by using RDF properties 
to relate these URIs, such as broader/narrower relations as first 
proposed in
http://dbooth.org/2007/splitting/#isBroaderThanDeclaration
and later defined slightly differently by the Provenance working group:
http://www.w3.org/ns/prov#specializationOf

The dilemma is that *every* new RDF statement that you make about a 
resource creates a "narrower contextual scope".  Thus, if we are to 
completely avoid this problem, we would have to mint a new URI every 
time we want to make any statements at all about :alansDad !   This 
certainly seems like a good approach in some cases -- as Jeremy 
suggested -- but I am not sure that it would be very palatable to do 
that every time you wish to use any URI.  Yet if you don't do that every 
time, then you run the risk of creating specializations that become 
inconsistent when they are merged, as previously discussed.

My guess at present is that the best approach is to try to choose a good 
balance between reusing existing URIs and minting new URIs with more 
specialized definitions.  But that's just a guess: I could certainly be 
convinced differently tomorrow.

David
Received on Monday, 18 March 2013 01:41:04 UTC

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