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

From: Enrico Franconi <franconi@inf.unibz.it>
Date: Tue, 30 Nov 2010 16:34:36 +0100
Cc: SPARQL Working Group <public-rdf-dawg@w3.org>
Message-Id: <1086E2DC-238E-4C81-BA95-87BB619BB506@inf.unibz.it>
To: Bijan Parsia <bparsia@cs.man.ac.uk>
On 30 Nov 2010, at 15:40, Bijan Parsia wrote:

>> uh? If you look at the model theory of RDF, being existentially bound is exactly the semantics of bnodes.
> Yes, but I think the proper way to treat bNodes is to willfully violate the spec.

Not at all. You think wrong.

> [snip]
>> As a theoretician, if you think to classical entailment as inclusion between models, then you have no other choice than to agree with me. 
> [snip]
> As an interested party, I really don't.

I guess that you implicitly admitted that *as a theoretician* the answer would be yes :-)

>>> And most users experience and expect the BNodes.
>> They can get them by using the OWL-DS entailment regime as defined in the current semantics.
> Since I think there are no other users, I really don't see the point of including the alternative.
> [snip]
> Right, and in my experience there are no such users. When users want/need existential semantics, they are happy to use a class expression. More complex patterns have absolutely no users.

A bit radical here. What about the OWL2-QL and OWL2-EL communities?

>> Without this addition, SPARQL2 can never be adopted by any of the DB centric applications based on ontology based access technology, since all of these technologies do assume BGPs with proper existential variables. We would loose the entire ontology-based DB integration market based on OWL-DL.
> I find this prima facie unbelievable. First, nothing prevents you from adding such a feature.

Interesting argument.

> It can be a nice differentiating feature, in fact.


> Proliferation of regimes is generally a negative. Futhermore, it might encourage people to implement something "because its in the standard" which I think is a waste. 
> I don't see the benefit. Indeed, I don't see the benefit to anyone.

The benefit is to allow, for example, OWL2-QL people to work using a standard as opposed to work by inventing their own syntax.

>> Be surprised: the academic, industry, and system people working on OWL-QL-based systems are already very upset by the limitation of the current version of the standard, and asked me to discuss the matter with the group.
> Can you put me in contact with them? Mediated communication isn't very efficient.

Ah, so you don't trust me.

Received on Tuesday, 30 November 2010 15:35:10 UTC

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