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Re: RDF Model Theory Working Draft: Comment

From: Graham Klyne <GK@ninebynine.org>
Date: Sun, 07 Oct 2001 09:33:29 +0100
Message-Id: <>
To: Arjun Ray <aray@nyct.net>
Cc: <www-rdf-comments@w3.org>
At 03:46 PM 10/6/01 -0400, Arjun Ray wrote:
>The problem is this: If an RDF graph has "one node for each uriref,
>bNode or literal identifier", then the general representation of a
>statement will need three nodes - not two - because all three of the
>triple's terms are *nodal*: the arc from subject to object allegedly
>corresponding to the triple is being labelled with a term that is
>already supposed to be (the label of) a node.  In short, how can the
>label of an arc be a URI (reference) that by definition has been
>mapped to a node already?

I think the answers are all in the model theory:

- A URI that labels an arc may or may not also label a node.

- Each URI is mapped to a resource

- Each node is mapped by the interpretation to a resource or literal 
value;  if the node is labelled by a URI then the corresponding resource if 
defined by the URI -> resource mapping (IS in the Model Theory).

- Each arc corresponds to a truth value defined by the existence of a 
member of the relational extension of a property resource;  the property 
resource is defined by the URI -> resource mapping of the arc label.

In all this, there is no requirement for an arc to be a node;  indeed that 
would be a contradiction of the syntactic definition of the graph.  A node 
labelled by a URI and an ARC labelled by the same URI are quite distinct in 
the domain of interpretation.


You cited:

>[3] http://lists.w3.org/Archives/Public/www-rdf-comments/1998JanMar/0002.html

I think those were legitimate and justified comments on the earlier RDF 
documents, which *have* been addressed by the model theory.


Graham Klyne
Received on Sunday, 7 October 2001 05:00:23 UTC

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