Re: mergeg in current Semantics ED

Le 07/03/2013 21:51, Pat Hayes a écrit :
>
> On Mar 7, 2013, at 12:30 PM, Peter Patel-Schneider wrote:
>
>>
>>
>> On Thu, Mar 7, 2013 at 10:22 AM, Pat Hayes <phayes@ihmc.us> wrote:
>>
>> On Mar 7, 2013, at 9:52 AM, Antoine Zimmermann wrote:
>>
>>> There is a problem with the definition of merge in the draft.
>>>
>>> I'm using math notations instead of a concrete serialisation
>>> syntax because I want to show things at the abstract syntax
>>> level, which is what RDF Semantics relies on.
>>>
>>> Let us take a blank node b from the set of blank nodes. Let us
>>> consider the two graphs G1 = {(<s1>,<p1>,b)} and G2 =
>>> {(<s2>,<p2>,b)}.
>>
>> You have the same bnode in both graphs, so they must be in the same
>> scope, right? For example, both are subgraphs of a larger graph, or
>> both in the same dataset.
>>
>>>
>>> Let us ask ourselves whether {G1,G2} entails:
>>>
>>> G = {(<s1>,<p1>,b),(<s2>,<p2>,b)}
>>>
>>> The answer is trivially NO wrt the current semantics of the ED.
>>
>> If those really are the same b, then the answer is YES, and I claim
>> that it should be.
>>
>>
>> I don't know how you are going to get this to go through.
>
> Do you mean, technically or politically? Technically, this is true
> now (that G1 and G2 together entail G) and it also was in the 2004
> semantics, if the G1 and G2 were for example subgraphs of G.

Huh? No. See proof in another email.


> Politically, I think we have debated this to death and the new
> account based on scopes is exactly what the WG wants.

Ah? I don't think there is a consensus on that.


> For example, we
> have an explicit decision that all bnodes in (all graphs in) a
> dataset shall share bnodes in common, so to standardize those bnodes
> apart would be definitely a mistake.

This has nothing to do with merge. RDF Datasets, as defined currently in 
RDF 1.1 Concepts and SPARQL, may or may not share bnodes, just like RDF 
Graphs, as defined currently in both RDF 2004 and in RDF 1.1 Concepts, 
may or may not share bnodes.

To standardise apart is not a problem since, as Peter mentioned earlier, 
reasoners have to standardise apart identifiers anyway.



AZ

>
> Pat
>
>
>>
>> peter
>>
>>
>
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-- 
Antoine Zimmermann
ISCOD / LSTI - Institut Henri Fayol
École Nationale Supérieure des Mines de Saint-Étienne
158 cours Fauriel
42023 Saint-Étienne Cedex 2
France
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http://zimmer.aprilfoolsreview.com/

Received on Friday, 8 March 2013 07:18:17 UTC