Prolog

Facts

    male(john).
    male(allen).
    female(timy).
    married(john, mary).
    child(allen, john).
    child(timy, john).
    child(timy, mary).

Rules

         Head           Body
    -------------    -----------
      mother(M,C) :- child(C,M),
                     female(M).

      father(F,C) :- child(C,F),
                     male(F).

      parent(P,C) :- child(C,P).

         son(S,P) :- child(S,P),
                     male(S).

    daughter(D,P) :- child(D,P),
                     female(D).

     sibling(X,Y) :- child(X,P),
                     child(Y,P),
                     not(X=Y).

Goals

    Verifier        married(john, mary).

    Finder          married(X, mary).

    Doer            write('End').