Prolog/Inference Engines

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By default Prolog does a top-down logic inference.

Example:

clever(joe).
handsome(joe).
 
hasgirlfriend(X):-
    clever(X),handsome(X).

We run this as "hasgirlfriend(X)." to get the people who have a girlfriend.

Bi-directional inference:

clever(joe).
handsome(joe).
 
rule([handsome(joe),clever(joe)],(hasgirlfriend(joe))).
 
run:- call(rule(X,Y)),findall(A,(member(A,X),call(A)),L),
	length(X,Rulelength),
	length(L,Rulelength),
	assert(Y),print(Y).

We run this as "run.".

We don't have to directly ask who has a girlfriend, it gives us all results that can be implied. The benefit of bidirectional inferencing is the speed gain.