[rules-users] One question about "NOT"

[Mark Proctor]

Senlin Liang wrote:
> Hi all,
>
> I checked the manual about "not", and it says:
> ==quote==
> not' is first order logic's Non-Existential Quantifier and checks for
> the non existence of something in the Working Memory. Think of 'not'
> as meaning "there must be none of...". "
> ==end==
>
> So there is no negation-as-failure, no stable model semantics, no well
> founded semantics in Drools. Is it the case?
>   
This is the standard way that a Production Rule system works, and often 
very hard for "formal" logiticians to understand, they get in a bit of a 
tizz about it - wanting it to work like prolog. When in reality the way 
production rules do 'not' is very practice for end users.

I'll be adding backward chaining later this year, the foundations are 
there, we can look into your issues as part of this if you like. If you 
can think how to improve standard PR behaviour, let me know.

Mark
> Thanks,
> Senlin
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