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Unique denotation assumption

From: David Booth <david@dbooth.org>
Date: Wed, 11 Sep 2013 21:14:23 -0400
Message-ID: <5231156F.3000906@dbooth.org>
To: Pat Hayes <phayes@ihmc.us>, www-archive <www-archive@w3.org>
hi Pat,

Since the RDF WG does not have a public discussion list to which 
non-members can post, I'm copying the public www-archive list.  I want 
to propose a couple of changes to the RDF specs, and thought it might 
save the WG and others time if I first discuss them with you (and anyone 
else you think would be interested).  One of them is the following.

In https://dvcs.w3.org/hg/rdf/raw-file/default/rdf-concepts/index.html
I see this statement:

   "IRIs have global scope: Two different appearances of an IRI
   denote the same resource."

This is wrong, because an IRI can and often does denote different 
resources in different RDF interpretations.  And this, in practice, 
means that an IRI often denotes different resources in different 
*graphs*, because any graph has a set of satisfying interpretations, and 
different graphs may have different sets of satisfying interpretations. 
  For example, suppose graphs g1 and g2 have sets of satisfying 
interpretations s1 and s2, respectively, and those sets may be disjoint. 
  Then colloquially (and technically) we can say that an IRI may map to 
one resource in g1 (i.e., in some interpretation in s1) and a different 
resource in g2 (i.e., in some interpretation in s2).

This requires thinking about graphs in terms of sets of satisfying 
interpretations -- an important and valid perspective -- rather than 
assuming that one looks at them only through the lens of a single 
interpretation.

In short, I think the above statement needs to be qualified somehow, 
such as:

   "IRIs are intended to have global scope: Two different
   appearances of an IRI are intended to denote the same resource.
   (But see RDF Semantics for caveats regarding different RDF
   interpretations.)"

And then we would have to add something to the RDF Semantics document to 
explain how an IRI can denote different things in different interpretations.

Does this make sense to you?  Comments?

David
Received on Thursday, 12 September 2013 01:14:51 UTC

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