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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":
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:
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":

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)

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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