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Re: Role of URI and HTTP in Linked Data

From: David Booth <david@dbooth.org>
Date: Thu, 11 Nov 2010 09:00:00 -0500
To: Jiří Procházka <ojirio@gmail.com>
Cc: nathan@webr3.org, public-lod@w3.org
Message-ID: <1289484000.5492.72800.camel@dbooth-laptop>
On Thu, 2010-11-11 at 07:23 +0100, Jiří Procházka wrote:
[ . . . ]
> I think it is flawed trying to enforce "URI == 1 thing" 

Exactly right.  The "URI == 1 thing" notion is myth #1 in "Resource
Identity and Semantic Extensions: Making Sense of Ambiguity":
http://dbooth.org/2010/ambiguity/paper.html#myth1 
It is a good *goal*, but it is inherently unachievable. 

> by some
> system (especially if you want to maintain RDF as one of supported
> structured data formats (I dare to say the major one)), as nothing can
> be completely unambiguous (in RDF) - that is something the publisher
> needs to keep in mind and work towards to.

Right.  And believe it or not, the RDF Semantics *already* accounts for
this inherent ambiguity by noting that an RDF graph will normally have
multiple interpretations.  (An "interpretation" of a graph in RDF
semantics is a mapping from its URIs to resources.)  To quote from the
RDF Semantics:
http://www.w3.org/TR/rdf-mt/#interp
[[
Notice that there is no presumption here that any assertion contains
enough information to specify a single unique interpretation. It is
usually impossible to assert enough in any language to completely
constrain the interpretations to a single possible world, so there is no
such thing as 'the' unique interpretation of an RDF graph.
]]

For a fairly clear explanation of how this works, see "Resource Identity
and Semantic Extensions: Making Sense of Ambiguity":
http://dbooth.org/2010/ambiguity/paper.html

The important thing to keep in mind is that ambiguity is *relative* --
it depends on the application.  An application that does not need to
differentiate the toucan from its web page will still produce correct
answers even if it uses a URI the ambiguously denotes both.  However,
another application that needs to associate a different :hasOwner
property value with the toucan than the web page will need to use a
different URI for each.



-- 
David Booth, Ph.D.
Cleveland Clinic (contractor)
http://dbooth.org/

Opinions expressed herein are those of the author and do not necessarily
reflect those of Cleveland Clinic.
Received on Thursday, 11 November 2010 14:00:29 UTC

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