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Re: safety and external predicates

From: Axel Polleres <axel.polleres@deri.org>
Date: Fri, 15 Aug 2008 09:40:11 +0100
Message-ID: <48A540EB.1080407@deri.org>
To: kifer@cs.sunysb.edu
CC: Gary Hallmark <gary.hallmark@oracle.com>, Chris Welty <cawelty@gmail.com>, "Public-Rif-Wg (E-mail)" <public-rif-wg@w3.org>

Michael Kifer wrote:
> I agree. I don't quite see what are we (or anybody) is going to gain from
> having this core dialect.

So far, I was working under the assumption that we had in mind with Core 
  a minimalistic fragment that is implementable.
It was mentioned several times at least, but I could have misunderstood 
or there might be diverging opinions in the group here.

If I got that correct, then we still might need clarification what 
people mean by "implementable"? I personally implied "implementable" 
would mean that any system needs to
a) be able to parse Core rulesets
b) show a well-specified behavior on "executing" Core rulesets.
As for b) if "well-specified behavior" includes not terminating, or 
crashing, fair enough.

If this understanding of b) is correct, then (how) does this affect the
whole Test cases discussion?

Thanks for clarification,

> michael
> On Thu, 14 Aug 2008 12:12:35 -0700
> Gary Hallmark <gary.hallmark@oracle.com> wrote:
>> I think a better use of the group's resources would be to work on 
>> dialects where there are real rules that could be interchanged.  For 
>> example, members might help push PRD along, start work on FOL, or even a 
>> SQL dialect.
>> Core is whatever turns out to be in the intersection of the standard 
>> dialects. 
>> Chris Welty wrote:
>>> I still am not convinced that safeness is anything more than an 
>>> academic requirement for CORE.  I would like to hear from someone who 
>>> is a) interested in CORE and b) has some idea what an implementation 
>>> is and c) has some idea what users of CORE would need, to let us know 
>>> if these requirements matter:
>>> 1) Decidability: is is important that RIF-Core have decidable 
>>> reasoning? That is, any compliant RIF-Core reasoner (implementation) 
>>> will be guaranteed to terminate on any rule-set?
>>> 2) If decidability is a requirement, is tractability?  That is, any 
>>> implementation will terminate in worst-case polynomial time (or better?)
>>> My general impression from talking to some potential RIF implementors 
>>> is that they treat rule-bases like programs - if your programs don't 
>>> work its your fault, go fix them.  However one important difference 
>>> between rule/logic "programs" and procedural programs is the amount of 
>>> control you have over the search strategy.  I think this is (a 
>>> practical reason) why decidability is considered by some to be 
>>> important for these languages and not for e.g. Java.
>>> -Chris
>>> 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=

Dr. Axel Polleres, Digital Enterprise Research Institute (DERI)
email: axel.polleres@deri.org  url: http://www.polleres.net/

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Received on Friday, 15 August 2008 08:40:58 UTC

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