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Fwd: Proposed change to the OWL-2 Direct Semantics entailment regime

From: Enrico Franconi <franconi@inf.unibz.it>
Date: Mon, 20 Dec 2010 10:48:50 +0100
Cc: Maurizio Lenzerini <lenzerini@dis.uniroma1.it>
Message-Id: <3491888A-8655-4490-9C57-6C88260ACB99@inf.unibz.it>
To: SPARQL Working Group <public-rdf-dawg@w3.org>
I forward this message I received from Maurizio Lenzerini.

Begin forwarded message:

> From: Maurizio Lenzerini <lenzerini@dis.uniroma1.it>
> Date: 20 December 2010 10:44:38 CET
> To: Enrico Franconi <franconi@inf.unibz.it>
> Subject: Re: Proposed change to the OWL-2 Direct Semantics entailment regime
> Reply-To: lenzerini@dis.uniroma1.it
> 
> Dear Enrico,
> 
> I talked with several people who use Quonto in real world applications, including:
> 
> Piero Poccianti <Piero.Poccianti@BancaToscana.it> from MPS
> Raffaele Vertucci <rvertucci@selex-si.com> from Selex SI
> Alfonso Amoroso <aamoroso@sesm.it> from Sesm
> Paolo Naggar <naggar.paolo@fastwebnet.it> consultant for CM Sistemi
> Floriana Di Pinto <dipinto@dis.uniroma1.it> consultant for Telecom Italia
> 
> and they were really surprised to hear that SPARQL might not support non-distinguished variables in conjunctive queries.
> 
> In all the applications mentioned above, there is a strong need of answering queries with non-distinguished variables. Just to name one interesting scenario where missing non-distinguished variables would be a real problem, consider checking quality/completeness of data.
> 
> The query:
> 
> { x,z | R1(x,y), R2(y,z) }
> 
> tells me which x and z are connected through y, without necessarily knowing who is the y. On the other hand, the query
> 
> { x,y,z | R1(x,y), R2(y,z) }
> 
> tells me for which x,z I KNOW the y.
> 
> The above queries show a case where, with the use of non-distinguished variables in conjunctive queries, I can figure out which information is missing from my data. Indeed, by comparing the answers to the above two queries, I can infer which information is missing!
> 
> In Quonto, the use of distinguished variables is essential! Probably, our users will not use a language without them!
> 
> Best.
> 
> --Maurizio
Received on Monday, 20 December 2010 09:49:26 GMT

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