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

From: Alan Ruttenberg <alanruttenberg@gmail.com>
Date: Tue, 12 Aug 2008 11:22:40 -0400
Message-Id: <BACE43AF-1765-485F-99DE-62EEC09EA526@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>
To: Ivan Herman <ivan@w3.org>

On Aug 12, 2008, at 11:16 AM, Ivan Herman wrote:

> 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:-(

Yes, but my question to Michael was to this point.  From what he says  
I don't see that the theoretical existence of an infinite number of  
triples necessitates their materialization by forward chaining. There  
are other methods of using rules.

-Alan

>
> 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
>>> Stiftung des bürgerlichen Rechts
>>> Az: 14-0563.1 Regierungspräsidium Karlsruhe
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>>> Studer
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>>> Leßnerkraus
>>>
>
> -- 
>
> 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 15:23:20 GMT

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