Re: adding existentials and conjunctions to BLD consequents

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
> 

-- 
                          debruijn@inf.unibz.it

Jos de Bruijn,        http://www.debruijn.net/
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