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Re: [PP] [ENT] Property paths and entailments

From: Andy Seaborne <andy.seaborne@talis.com>
Date: Fri, 28 May 2010 11:06:58 +0100
Message-ID: <4BFF95C2.3060202@talis.com>
To: Ivan Herman <ivan@w3.org>
CC: W3C SPARQL WG <public-rdf-dawg@w3.org>


On 28/05/2010 9:13 AM, Ivan Herman wrote:
>
> (Lee asked to have different threads to different issues, so here I am)
>
> The question was:
>
> [[[
> + How do property paths interact with entailment? Discussion is needed with the members of the WG most swapped in with the entailment work.
> ]]]
>
> My (mental) model has always been that the entailment regime (in principle) expands all graphs to new graphs that include the original graph plus all possible extra triples that the entailment regime produces, and the query itself is performed on this expanded graph. If this model is right, then the natural way of looking at this is that the property path expansions are performed on the entailed graph.
>
> Do I miss some major issue here?

It certainly ought to look like that for entailment regimes where there 
is a concrete logical closure.

Thing I can think of (so this is not trying to be an exclusive list of 
all the issues, which is why I think it need TF-ENT and TF-PP):

1/ Suppose we have:
     { :?x :p{2} ?y . }
which should be
     { :?x :p ?z . ?z :p ?y }
with ?z projected away.

Does introducing that variable and hiding it again present a problem?
What if it were _:z and not ?z?

     { :?x :p [ :p ?y ] }

2/ There is overlap with :p* and transitive properties as well as 
property chains.

On one side, the application writer is trying to get some effect, and on 
ths otehr side the data publisher, through the ontology, may be getting 
the same effect.  What happens?


I put the area of PP+ENT down as an issue to make sure we are all aware 
that here is something here to be checked and I hope it's not a 
fundamental problem.

	Andy
Received on Friday, 28 May 2010 10:07:27 GMT

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