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Re: [Graphs] g-snap vs. g-box and graph equality

From: Peter Frederick Patel-Schneider <pfps@research.bell-labs.com>
Date: Thu, 7 Apr 2011 09:28:34 -0400
Message-ID: <20110407.092834.1335974459910758053.pfps@research.bell-labs.com>
To: <dpw@talis.com>
CC: <lee@thefigtrees.net>, <alexhall@revelytix.com>, <public-rdf-wg@w3.org>
From: David Wood <dpw@talis.com>
Subject: Re: [Graphs] g-snap vs. g-box and graph equality
Date: Thu, 7 Apr 2011 07:56:53 -0500

> On Apr 6, 2011, at 23:37, Lee Feigenbaum <lee@thefigtrees.net> wrote:
> 
>> On 4/6/2011 11:30 PM, Alex Hall wrote:
>>> Just trying to get a handle on people's expectations around named graphs
>>> as g-snaps vs. g-boxes as it relates to graph equality (and inequality).
>>> 
>>> Given the two notional TriG/Qurtle fragments which we would like to combine:
>>> 
>>> file-1.trig:
>>> :G1 { :a :b :c } .
>>> :G2 { :d :e :f } .
>>> 
>>> file-2.trig:
>>> :G1 { :a :b :d } .
>>> :G3 { :d :e :f } .
>>> 
>>> My impression so far is that some people want to treat named graphs as
>>> g-snaps, and some as g-boxes.  Suppose for a second that we treat them
>>> as naming g-snaps.  Without expressing an opinion one way or another, I ask:
>>> 
>>> 1.  Is the fact that G1 is mapped to two different g-snaps an inconsistency?
>>> 
>>> 2.  From the fact that G2 and G3 are mapped to the same g-snap, can we
>>> conclude that G2 and G3 are in fact the same resource?
>> 
>> I'm guessing that because of the OWA that the answer to both is "no",
>> though I'm not really sure? 
> 
> I certainly hope that the answer to both is 'no'.
> 
> Regards,
> Dave

Absent some semantics I don't see that the present tense can be used
here.  Absent some desiderata I don't see that this can even be weakened
to the future subjunctive.  Of course, it is always possible to hope
that for a particular answer to be true in the future.

The thorny issues that have to be worked out include things like whether
RDF can exactly specify the contents of a named graph, and, if so, how.
If the above indeed exactly specifies the contents of a named graph,
then it better be the case that the two documents above are not
consistent with each other, in a fashion similar to the two triples
  <ex:a> <ex:p> "<notLegalXML"^^rdf:XMLLiteral .
and
  <ex:p> rdfs:range rdf:XMLLiteral .
not being consistent with each other in RDFS.

peter
Received on Thursday, 7 April 2011 13:29:25 GMT

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