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Re: safety and external predicates

From: Jos de Bruijn <debruijn@inf.unibz.it>
Date: Tue, 12 Aug 2008 18:31:08 +0200
Message-ID: <48A1BACC.4040502@inf.unibz.it>
To: RIF WG <public-rif-wg@w3.org>



Jos de Bruijn wrote:
> 
> It seems to me that if we want to have a notion of safeness in Core, we 
> would want something like "domain-safeness" as described in [2] (page 281).
> Essentially, it ensures that there is no recursion involving variables 
> that do not occur in user-defined predicates in the body.  This ensures 

s/do not/do/

> finiteness.
> 
> So, it would not be possible to write:
> p(x) :- p(y), External(add(y,1,x))
> p(1)
> (which is the example Axel gave in the telephone conference today, and 
> which leads to an infinite extension of P)
> 
> But it would be possible to write:
> q(x) :- p(y), External(add(y,1,x))
> p(1)
> because there is no recursive dependency between q and any of the body 
> predicates
> 
> 
> Best, Jos
> 
> Axel Polleres wrote:
>>
>> Two pointers here... the notion of strong safety in hex-programs [1,2] 
>> and Topor's considerations on  safe database queries with arithmetics 
>> [3] (cudos jos for the latter one)
>>
>>
>> 1. R. Schindlauer. Answer-Set Programming for the Semantic Web. PhD 
>> thesis, Vienna University of Technology, Dec. 2006.
>> http://www.kr.tuwien.ac.at/staff/roman/papers/thesis.pdf
>>
>> 2.  Thomas Eiter, Giovambattista Ianni, Roman Schindlauer, and Hans 
>> Tompits. Effective Integration of Declarative Rules with External 
>> Evaluations for Semantic Web Reasoning. In York Sure and John 
>> Domingue, editors, Proceedings of the 3rd European Conference on 
>> Semantic Web (ESWC 2006), Budva, Montenegro, number 4011 in Lecture 
>> Notes in Computer Science (LNCS), pages 273-287. Springer, June 2006.
>> http://www.springerlink.com/content/f0x23wx142141v44/
>>
>> 3. R. Topor. Safe database queries with arithmetic relations (1991)
>> Proc. 14th Australian Computer Science Conf 
>> http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.48.4845
>>
>>
> 

-- 
Jos de Bruijn            debruijn@inf.unibz.it
+390471016224         http://www.debruijn.net/
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Received on Tuesday, 12 August 2008 16:31:05 GMT

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