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Re: adding existentials and conjunctions to BLD consequents

From: Jos de Bruijn <debruijn@inf.unibz.it>
Date: Fri, 23 May 2008 16:17:44 +0200
Message-ID: <4836D208.70705@inf.unibz.it>
To: Sandro Hawke <sandro@w3.org>
CC: public-rif-wg@w3.org
> I'm afraid that adding existentials to rule heads pushes the language 
> outside of Horn.  In fact, we would nearly have full first-order logic 
> (the only thing that is missing is destruction); not a rule language.

s/destruction/disjunction/

This was a speech recognition error, and I neglected to read over the 
text before sending it off.  So, the Freudian slip was by my (perhaps 
not unintelligent) speech recognition system :-)

Best, Jos

> Adding conjunction to rule heads is not a problem, because conjunctions 
> can be split into several rules with atomic formulas in the heads.
> 
> Best, Jos
> 
> Sandro Hawke wrote:
>> In planning to implement RIF for N3, the two extensions I mostly need
>> are to allow existentials and conjunctions in the the rule consequents.
>> These are straightforward extensions, with nice fallback rewrites, but I
>> thought I would just raise the question of putting them directly in BLD.
>>
>> I note, in particular, that Production Rule systems want something very
>> much like existentials in the consequent, too, so this might possibly
>> even go into Core.  But maybe it's not exactly the same thing, and
>> datalog certainly doesn't have it.
>>
>> I'm fine working with this as just an extension, but I thought I should
>> at least raise the issue in case anyone else is sympathetic.
>>
>>      - Sandro
>>
> 

-- 
                          debruijn@inf.unibz.it

Jos de Bruijn,        http://www.debruijn.net/
----------------------------------------------
One man that has a mind and knows it can
always beat ten men who haven't and don't.
   -- George Bernard Shaw


Received on Friday, 23 May 2008 14:18:25 GMT

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