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Re: Labelled graphs

From: Sandro Hawke <sandro@w3.org>
Date: Tue, 24 Apr 2012 08:04:41 -0400
To: Andy Seaborne <andy.seaborne@epimorphics.com>, Guus Schreiber <guus.schreiber@vu.nl>
Cc: public-rdf-wg@w3.org
Message-ID: <1335269081.9663.17.camel@waldron>
(mostly agreement, a few details)

On Tue, 2012-04-24 at 12:03 +0100, Andy Seaborne wrote:
> 
> On 17/04/12 16:59, Guus Schreiber wrote:
> ...
> 
> > An attempt at formulating a possible conclusion/consensus from this thread:
> >
> > * Non-typed labels are simply associations, no special semantics

There are some semantics, though: the label IRI (or blank node) denotes
something (maybe call it a "labeling object"), and that something is
associated with the graph.   This differs from SPARQL Datasets, where
the label IRI is directly associated with the graph.

The difference doesn't show up in normal SPARQL, but would be visible if
there was reasoning, such as with owl:sameAs.   See these test cases:
http://www.w3.org/2011/rdf-wg/wiki/Graphs_Design_6.1#Graph_Labels

> > * Typed labels: we do not seem to come up with more than these two:
> >
> > 1. The label is typed as a rdf:StaticGraphContainer:
> > the graph labeled is a g-snap of the label URL

I'm not convinced we can make this kind of definition work right, but
I'm not opposed to trying.  It will have to bring TAG language into the
RDF specs for the first time.   I'm also not sure we need "Static",
since the RDF view is still that the universe is static. 

> > 2. The label is types as a rdf:Graph:
> > the label denotes the graph it labels

Yes.

> > * When the same label is used multiple times in the same dataset, the
> > graph is
> > assumed to be the union of the graphs labeled with it

This is the "partial-graph semantics" view, which I can live with, but
some people have expressed opposition.  We should probably try some
straw polling on it.

> > The appears to be in line to the 6.1 design, with some
> > modifications/specializations.

I wonder if we can't adopt something close to 6.1, close pretty much all
the open GRAPHS issues, then open a few new ones, like
partial-vs-complete-graph semantics and whether/how to define
GraphContainer.

    -- Sandro

> > Guus
> 
> (sorry for the delay - was not at work)
> 
> Guus - nice summary.
> 
> 	Andy
> 
> 
> 
Received on Tuesday, 24 April 2012 12:04:58 UTC

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