Re: New proposal for the semantics

More thoughts

On 15/11/2021 13:32, Pierre-Antoine Champin wrote:
> (...)
>
> More precisely, what we have is
>
>   :markus a :penguin.
>   :tweety :can :fly.
>   { :tweety a :penguin } => { :tweety :can :fly }.
> |=
>   :markus a :penguin.
>   ?x :can :fly.
>   { ?x a :penguin } => { ?x :can :fly }.
>
> From this, it would seem that we must infer that :markus :can :fly. 
> That would be a problem (as it is clearly not the intent of the first 
> graph), but the problem is actually elsewehere. There exists a model 
> of the 2nd graph (e.g. the Herbrand model of the 1st one) in which 
> :markus can not fly. So ":markus :can :fly" is not entailed by the 
> first graph (which is ok) but not entailed either by the 2nd one 
> either (which is a problem). So rule-entailment actually fails to 
> capture the semantics of rules :-(
>
> Thanks for pointing that out. This is a bit frustrating, but that's 
> progress ;-)
>
My gut feeling is that this issue is causes by the merging of blank 
nodes and quick vars into a single kind of variables... Handling them 
differently might help solve this problem. I'll think about it.

   pa