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Re: ACTION-178: What is ISSUE-116 (Axiomatic Triples for OWL R) about?

From: Ivan Herman <ivan@w3.org>
Date: Tue, 12 Aug 2008 17:16:16 +0200
Message-ID: <48A1A940.2030409@w3.org>
To: Alan Ruttenberg <alanruttenberg@gmail.com>
CC: Michael Schneider <schneid@fzi.de>, public-owl-wg Group WG <public-owl-wg@w3.org>, Zhe Wu <alan.wu@oracle.com>, Ian Horrocks <ian.horrocks@comlab.ox.ac.uk>


Alan Ruttenberg wrote:
> 
> On Aug 12, 2008, at 11:02 AM, Michael Schneider wrote:
> 
>> Alan Ruttenberg wrote:
>>
>>> Is the assumption that in OWL R/Full that the only way in which one
>>> determine entailments is to forward chain rules and then look in the
>>> resultant triples for it?
>>
>> It's not an "execution semantics". Instead, there has to *exist* a finite
>> sequence of rule applications, which leads from the LHS to the RHS (or an
>> upper graph of the RHS).
> 
> OK. I'm then confused by Ian's comment about generating infinite numbers 
> of triples:
> 

But his comment _was_ justified. In

http://www.w3.org/TR/rdf-mt/#RDFINTERP

the number of axiomatic triples is infinite indeed, due to the rdf:_i 
terms. Herman ter Horst's trick of keeping it finite for a specific 
graph tries to get around that problem and thereby making it possible to 
do, eg, a forward chaining on a specific graph (with the caveat that 
PFPS just referred to in another mail:-(

Ivan


>> Presumably, making axiomatic triples be part of OWL RL (Full) would 
>> mean extending the rule set so that it would generate such triples. 
>> There could be a very large (perhaps even infinite) number of such 
>> triples. This might be a serious burden on implementations and lead to 
>> a significant degradation in performance.
> 
> 
> 
>> "Entailment" might be not the right term here, because it is probably 
>> more
>> typically used in the context of model-theoretic semantics. I prefer 
>> to speak about "derivations".
> 
> We need to figure out and use a common language or make the appropriate 
> language visible in the specification  if it is missing.
> 
> -Alan
> 
>>
>>> -Alan
>>
>> Cheers,
>> Michael
>>
>> -- 
>> Dipl.-Inform. Michael Schneider
>> FZI Forschungszentrum Informatik Karlsruhe
>> Abtl. Information Process Engineering (IPE)
>> Tel  : +49-721-9654-726
>> Fax  : +49-721-9654-727
>> Email: Michael.Schneider@fzi.de
>> Web  : http://www.fzi.de/ipe/eng/mitarbeiter.php?id=555
>>
>> 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
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>>
> 

-- 

Ivan Herman, W3C Semantic Web Activity Lead
Home: http://www.w3.org/People/Ivan/
PGP Key: http://www.ivan-herman.net/pgpkey.html
FOAF: http://www.ivan-herman.net/foaf.rdf



Received on Tuesday, 12 August 2008 15:16:48 GMT

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