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Re: Re: LC Comment on Entailment Regimes: Class and Property Variables take DL regime beyond FOL

From: Michael Schneider <schneid@fzi.de>
Date: Sun, 20 Nov 2011 11:02:40 +0100
Message-ID: <4EC8D040.4040009@fzi.de>
To: <public-rdf-dawg-comments@w3.org>
CC: Birte Glimm <birte.glimm@comlab.ox.ac.uk>
Dear SPARQL Working Group,

I think, the section on "Higher Order Queries" now contains
sufficient explicit discussion of the matter of variables
in class or property position, so implementers will become
aware of the issue when reading the specification.

My only concern was that the issue should be explicitly
mentioned. I did not ask for a discussion of optimized
implementation techniques, which I would consider out of
scope for a specification document.

Hence, I acknowledge that my comment was addressed.

Regards,
Michael

Am 10.11.2011 schrieb Birte Glimm:
> Michael,
>
> Thank you for your comment about the SPARQL Entailment Regimes document.
>
> Although the Direct Semantics Entailment Regime seems to allow for
> higher order queries, the restriction that variables can only bind to
> a finite set of names (such as class, property, or individual names)
> means that even queries that seem to be higher order (as the subclass
> query in the example in Sec. 6.4) can still be reduced to standard
> first-order queries. In particular, one can answer such a query by
> checking whether each of the finitely many instantiations of the query
> (where class variables are replaced by class names from the queried
> ontology, etc) are entailed by the queried ontology under OWL's Direct
> Semantics.
>
> We tried to make it clearer in Sec. 6.4 that no higher order reasoning
> is required to answer SPARQL queries with the Direct Semantics
> entailment regime. We do not think that discussing optimized
> implementation techniques that go beyond entailment checking can be
> discussed in the specification.
>
> We hope that this answer addresses your comment and would be grateful
> if you would acknowledge this by sending a reply to this mailing list.
>
> Birte, on behalf of the SPARQL-WG
>
> On 26 July 2011 13:02, Michael Schneider<schneid@fzi.de>  wrote:
>> Dear all!
>>
>> Document: SPARQL 1.1 Entailment Regimes
>> State: LCWD
>>
>> The first paragraph in Chap. 6 "OWL 2 Direct Semantics Entailment Regime"
>> states that variables are allowed in place of class names and property
>> names. Nothing is said, however, about what the semantic consequences are of
>> such enhanced flexibility.
>>
>> If one tries to conservatively extend the OWL 2 Direct Semantics [1] to
>> support such queries, the only way I see is to do this by a translation into
>> quantifying over variables for unary and binary relations (note that under
>> the Direct Semantics, classes and properties are sets and binary relations,
>> respectively). In other words, such a semantics goes beyond first-order
>> logic (FOL). This is significant, as the OWL 2 Direct Semantics was designed
>> as a fragment of standard FOL.
>>
>> I do not suggest to change the current specification, since I consider
>> variables in class and property position to be useful. What I suggest is to
>> make the "non-FOL issue" explicit in the document, to make implementers
>> aware of it. I suggest to put such a discussion in Sec. 6.4, which is
>> already dedicated to "Higher Order Queries", but does not treat this issue.
>>
>> [1]<http://www.w3.org/TR/2009/REC-owl2-direct-semantics-20091027/>
>>
>> Best regards,
>> Michael
>>
>> --
>> Dipl.-Inform. Michael Schneider
>> Research Scientist, Information Process Engineering (IPE)
>> Tel  : +49-721-9654-726
>> Fax  : +49-721-9654-727
>> Email: michael.schneider@fzi.de
>> WWW  : http://www.fzi.de/michael.schneider
>> ==============================================================================
>> FZI Forschungszentrum Informatik an der Universität Karlsruhe
>> Haid-und-Neu-Str. 10-14, D-76131 Karlsruhe
>> Tel.: +49-721-9654-0, Fax: +49-721-9654-959
>> Stiftung des bürgerlichen Rechts
>> Stiftung Az: 14-0563.1 Regierungspräsidium Karlsruhe
>> Vorstand: Dipl. Wi.-Ing. Michael Flor, Prof. Dr. rer. nat. Ralf Reussner,
>> Prof. Dr. rer. nat. Dr. h.c. Wolffried Stucky, Prof. Dr. rer. nat. Rudi
>> Studer
>> Vorsitzender des Kuratoriums: Ministerialdirigent Günther Leßnerkraus
>> ==============================================================================
>>
>>
>
>
>

-- 
Dipl.-Inform. Michael Schneider
Research Scientist, Information Process Engineering (IPE)
Tel  : +49-721-9654-726
Fax  : +49-721-9654-727
Email: michael.schneider@fzi.de
WWW  : http://www.fzi.de/michael.schneider
==============================================================================
FZI Forschungszentrum Informatik an der Universität Karlsruhe
Haid-und-Neu-Str. 10-14, D-76131 Karlsruhe
Tel.: +49-721-9654-0, Fax: +49-721-9654-959
Stiftung des bürgerlichen Rechts
Stiftung Az: 14-0563.1 Regierungspräsidium Karlsruhe
Vorstand: Dipl. Wi.-Ing. Michael Flor, Prof. Dr. rer. nat. Ralf Reussner,
Prof. Dr. rer. nat. Dr. h.c. Wolffried Stucky, Prof. Dr. rer. nat. Rudi 
Studer
Vorsitzender des Kuratoriums: Ministerialdirigent Günther Leßnerkraus
==============================================================================
Received on Sunday, 20 November 2011 10:03:18 GMT

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