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Re: why I don't like named graph IRIs in the DATASET proposal

From: Richard Cyganiak <richard@cyganiak.de>
Date: Sat, 1 Oct 2011 13:22:13 +0100
Cc: "public-rdf-wg@w3.org" <public-rdf-wg@w3.org>
Message-Id: <0D570518-6006-49E7-B248-0BA119878D91@cyganiak.de>
To: Pierre-Antoine Champin <pierre-antoine.champin@liris.cnrs.fr>
On 30 Sep 2011, at 13:49, Pierre-Antoine Champin wrote:
> The default graph contains:
> 
>  <http://example.org/bob>    dc:publisher  "Bob" .
> 
> which means that the *resource denoted* by <http://example.org/bob> is
> related to the string "Bob" by the relation denoted by predicate
> dc:publisher. It is *not* the IRI "http://example.org/bob" which is
> related to "Bob", but a *resource*.

Yes. <http://example.org/bob> is an IRI that denotes some entity, and that entity was published by Bob.

>  <http://example.org/bob>    dc:publisher  "Bob" .
> 
> If I knew another IRI for that resource, I could rewrite that triple
> 
>  <http://example.other.com/bob>  dc:publisher  "Bob" .
> 
> without changing the meaning of that triple in any way.

This is wrong on so many levels. I don't even know where to start.

Names matter. They are not interchangeable. They never are.

Just because *you* know that <bob> and <otherbob> denote the same entity, doesn't mean that anyone else knows it.

The RDF model theory document doesn't include a theory of reference – it doesn't explain how IRIs acquire their referents, or how entity acquire identifiers. So when you say, “if I knew another IRI for the same resource”, you've stepped outside of the account of “meaning” provided in that document.

> So the only way for this triple to provide information about a graph in
> the dataset is that the graph be in fact associated with the *resource*
> and not the IRI.

The triple provides information about an entity of unspecified nature. It says that this entity was published by Bob. The entity is known to be denoted by an IRI that is also used as a graph name in the dataset. As a convention it seems quite reasonable and useful to make the assumption that the mysterious entity denoted by the IRI is actually the graph.

But I think we can leave this association in the same nebulous realm of convention and social contracts as the association between IRIs and their referents in RDF in general.

Best,
Richard
Received on Saturday, 1 October 2011 12:22:55 GMT

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