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Re: some GRAPHS strawpolls for today (agenda?)

From: Steve Harris <steve.harris@garlik.com>
Date: Wed, 25 Apr 2012 19:11:17 +0100
Cc: public-rdf-wg <public-rdf-wg@w3.org>
Message-Id: <C4E9FD54-A00B-4D9E-97E1-DF6723B71392@garlik.com>
To: Sandro Hawke <sandro@w3.org>
On 25 Apr 2012, at 15:08, Sandro Hawke wrote:

> If we're going to talk about graphs today, maybe we can do it in a
> series of decisions.   There's not enough notice to make these binding,
> of course, but maybe we can get a sense of how close we are to
> consensus.
> If we can't even get consensus on a few of these, these I think we
> should stop working on graph semantics in this WG.  I hope we're very
> close to consensus on all of these, except maybe the last, which I could
> see continuing as an open issue well into CR.
> I've erred on the side of brevity here.
>     -- Sandro
> ====================================
> 1. The default graph is asserted
>  "{<a> <b> <c>}" entails turtle("<a> <b> <c>")


> 2. Named graphs are not asserted
>  "<u> {<a> <b> <c>}" does not entail turtle("<a> <b> <c>")


> 3. Named graphs are opaque
>  "<u> {<a> <b> <c>}"  does not entail "<u> {<a> <b> _:x}"

Surely it must if _:x is an existential variable?

> 4. Graph labels denote just like in RDF
>  "{<u1> owl:sameAs <u2>} <u1> {<a> <b> <c>}"
>  owl-entails
>  "<u2> {<a> <b> <c>}"

This seems like an OWL question, which http://www.w3.org/TR/sparql11-entailment/ should answer.

> 5. Blank nodes labels have file scope
>   See SPARQL queries in 
>   http://www.w3.org/2011/rdf-wg/wiki/Graphs_Design_6.1#Blank_Nodes
>   or Skolemization example in
>   http://lists.w3.org/Archives/Public/public-rdf-wg/2012Apr/0132.html

Ideally not, for various pragmatic reasons, but it wouldn't be a disaster. Just irritating.

> 6. In trig, @union can be used in place of the default graph
>   "@union <u> {<a> <b> <c>}" entails turtle "<a> <b> <c>"

I don't see why a data file should (or can) affect query engine operation. What happens if you ingest two files with different directives?

> 7. Datasets only say which triples are known to be in a named graph,
>   not which triples are *not* in that named graph.
>   The merge of "<u> {<a> <b> <c>}" and "<u> {<a> <b> <d>}" is 
>   "<u> {<a> <b> <c>,<d>}".  
>   Also "<u> {<a> <b> <c>,<d>}" entails "<u> {<a> <b> <c>}".


- Steve

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Received on Wednesday, 25 April 2012 18:11:57 UTC

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