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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 15:51:16 +0200
Message-ID: <4836CBD4.9090909@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.
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


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 13:52:15 UTC

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