Re: Possible incorrect test case (?)

Michael,

Thank you for this clear explanation.

It is now clear to me that WebOnt-Restriction-005 is a positive 
entailment under the Direct Semantics and a negative entailment under 
the RDF-based Semantics.

In which case the result of WebOnt-Restriction-005 should be reversed: 
HermiT passes the test and Pellet fails because they both implement the 
Direct Semantics.

Regards,
AZ.


Michael Schneider wrote:
> Hi!
> 
> This test case [1] really shows a non-entailment under the 
> OWL 2 RDF-Based Semantics (and also in OWL 1 Full). This is 
> a subtle problem coming from the RDF Semantics. 
> 
> The "lethal" bit is that the left-hand side graph of the test 
> does not contain the name "c". Since the LHS graph is satisfiable 
> under the RDF-Based Semantics, there exists an 
> OWL 2 RDF-Based interpretation I that satisfies the LHS graph 
> without having "c" in its (I's) vocabulary. According to the 
> 5th semantic condition "for ground graphs" in Section 1.4 of the 
> RDF Semantics [2], this interpretation will fail to satisfy
> the RHS of the entailment query, since the RHS contains a triple 
> in which the name "c" occurs.
> 
> But even if the mentioned semantic condition for RDF Simple Entailment
> would not be applicable, there would still be a different approach to 
> show the non-entailment-ness: Let's again start from the above 
> interpretation I (without the name "c" in the vocabulary), and 
> construct a new interpretation I* from I by only adding the name "c" 
> to the vocabulary of I*, where I*(c) denotes an individual in 
> the /complement/ of the set of all classes (i.e. "c" is not a class). 
> I* will still be an OWL 2 RDF-Based interpretation and will still 
> satisfy the LHS graph. But I* will /not/ satisfy the RHS graph, since 
> for this to hold the name "c" would be required to denote a class 
> (see Section 5.3 in the RDF-Based Semantics [3], the table entry for 
> property "owl:allValuesFrom").
> 
> So, in any case, there exists an OWL 2 RDF-Based interpretation that 
> satisfies the LHS but not the RHS of the test case. Hence, the 
> test case is a non-entailment for the RDF-Based Semantics.
> 
> The "correspondence theorem" [4] between the OWL 2 Direct Semantics 
> and the OWL 2 RDF-Based Semantics counters this problem (at least 
> for valid OWL 2 DL test cases) by replacing the original 
> entailment-query by a new one that mentions all names that 
> occur in the RHS also in the LHS, together with the correct typing 
> information (aka declaration). This is part of what is called 
> "balancing" in the proof of the theorem [5].
> 
> Best,
> Michael
> 
> [1]
> <http://km.aifb.uni-karlsruhe.de/projects/owltests/index.php/TestCase:WebOnt
> -Restriction-005>
> [2] <http://www.w3.org/TR/rdf-mt/#gddenot>
> [3]
> <http://www.w3.org/2007/OWL/wiki/RDF-Based_Semantics#Semantic_Conditions_for
> _the_Vocabulary_Properties>
> [4]
> <http://www.w3.org/2007/OWL/wiki/RDF-Based_Semantics#Correspondence_Theorem>
> [5] <http://www.w3.org/2007/OWL/wiki/RDF-Based_Semantics#def-balanced>
> 
>> -----Original Message-----
>> From: public-owl-wg-request@w3.org [mailto:public-owl-wg-request@w3.org]
>> On Behalf Of Mike Smith
>> Sent: Thursday, June 11, 2009 3:35 PM
>> To: Ian Horrocks
>> Cc: Antoine Zimmermann; W3C OWL Working Group
>> Subject: Re: Possible incorrect test case (?)
>>
>> On Wed, Jun 10, 2009 at 19:45, Ian
>> Horrocks<ian.horrocks@comlab.ox.ac.uk> wrote:
>>> It isn't obvious to me why this wouldn't be an entailment under the
>>> RDF-Based semantics -- at least not at this time of night. Can you
>> explain?
>>
>> I was basing this on the conclusion we drew when discussing the test
>> case
>>
>> http://km.aifb.uni-
>> karlsruhe.de/projects/owltests/index.php/TestCase:WebOnt-Class-005
>>
>> in January [1] -  that the definition of entailment in the OWL 1 Full
>> semantics and the OWL 2 RDF Based Semantics does not permit the
>> entailed ontology to use vocabulary not present in the premise
>> ontology. This led to the description in the Direct Semantics version
>> of the test
>>
>> http://km.aifb.uni-
>> karlsruhe.de/projects/owltests/index.php/TestCase:WebOnt-Class-005-
>> direct
>>
>> At present, after digging some I cannot support this position with
>> text from the specifications.  It may be that we assumed it to hold
>> because the alternative was that the WebOnt group had incorrectly
>> labeled and approved these test cases.  I'm now leaning toward the
>> latter view.
>>
>> Can someone more familiar with the OWL 1 Full and OWL 2 RDF-Based
>> semantics (e.g., Peter or Michael) refer to the text and come back
>> with a conclusive answer for the RDF-Based semantics versions of these
>> cases?
>>
>> Thanks,
>> --
>> Mike Smith
>>
>> Clark & Parsia
>>
>> [1] http://lists.w3.org/Archives/Public/public-owl-wg/2009Jan/0031.html
> 
> --
> Dipl.-Inform. Michael Schneider
> Research Scientist, Dept. 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
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> 


-- 
Antoine Zimmermann
Post-doctoral researcher at:
Digital Enterprise Research Institute
National University of Ireland, Galway
IDA Business Park
Lower Dangan
Galway, Ireland
antoine.zimmermann@deri.org
http://zimmer.aprilfoolsreview.com/

Received on Friday, 12 June 2009 13:07:59 UTC