prologmulti-agent

Simple Prolog implement about multi-agent argumentation


New to logic programming (Prolog). Come across a simple question but dont know how to code it in prolog.

Question is like you have several arguements: argument(a),argument(b)..., and several attack relations like attack(a,b) which means argument a attacks argument b. So given an argument I want to find out if it is a grounded one. "Grounded" for an argument a means if b attacks a, then there exists another argument, say c attacks b. If no argument attacks c then we say a and c are grounded.

Can you give an example how to implement this grounded/1 program to achieve this goal.

Not sure I make it clear....But welcome to give any advice (or code)!!


Solution

  • What I've understand from your explanation, an argument is grounded when there are no other grounded arguments attacking it.

    You can define a procedure grounded/1 which obeys this rule straightforward in prolog:

    grounded(A):-
      argument(A),    % A is an argument
      \+              % for which there does not exist
      (
        attack(B, A), % an attacker
        grounded(B)   % which is grounded
      ).
    

    [Edit after comment by OP]: If you have to deal with cycles, then you will probably need to keep a list of visited "attacks", no forbid cycles:

    grounded(A):-
      grounded(A, []).
    
    
    grounded(A, L):-
      argument(A),
      \+
      (
        attack(B, A),
        \+ member(B, L),  % Here we forbid cycles
        grounded(B, [A|L])  % We add the current argument to the list of forbidden arguments
      ).