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Re: Attempt to provide semantics to Sandro's named graph design

From: Sandro Hawke <sandro@w3.org>
Date: Tue, 10 Apr 2012 18:49:11 -0400
To: Ivan Herman <ivan@w3.org>
Cc: W3C RDF WG <public-rdf-wg@w3.org>
Message-ID: <1334098151.2249.80.camel@waldron>
On Tue, 2012-04-10 at 15:42 +0200, Ivan Herman wrote:
> Guys,
> 
> As a submission to tomorrow's discussion: I have tried to put some semantics 'meat' on the Sandro's skeleton design[1]. I have put it onto the wiki:
> 
> http://www.w3.org/2011/rdf-wg/wiki/Graphs_Design_6.1/Sem
> 
> it may provide a way to fold all this into the RDF Semantics with, I believe, a minimal amount of change to the current RDF Semantics (which is a plus for me!), pretty much as a separate section instead of rewriting the whole thing. It may also help in formulating some of the open issues.
> 
> I believe it reflects what Sandro thinks although I may of course be wrong...

Thanks.

I'm not fluent with formal semantics, but Eric and I took a look at this
and tried to make sense of it.   A few thoughts:

* Condition 1 -- shouldn't that be the "range" of I, not the "domain"?
That is, the graphs are in the set of things "I" maps to, not the things
"I" maps from.

* Condition 3 - I agree with Andy -- this condition doesn't belong

* Condition 4 -- I don't think it's correct to say there can only be one
name for a graph, which you're doing with the exclamation point.  I
don't see any need to say a name exists at all.  Can't we just say:

        all i in (1...n): <I(ui),Gi> in IEXT(I(rdf:hasGraph))

If I understand the notation right, that's what I had in mind.

* I think we want another condition that says a given label can only be
associated with one graph.   I'm not sure if we say that in the DS
conditions and in merging, or somehow say it globally.    Anyway, it
would be something like:

  all i,j in (1...n): if (ui,Gi) in DS and 
                          (uj,Gj) in DS and
                           ui = uj
                         then Gi=Gj.



That's it for now...

   -- Sandro
Received on Tuesday, 10 April 2012 22:49:15 GMT

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