law(external,language(prolog))


sent(X,release(M,H,P),Y):-do(release(X,M,[H,P])).
sent(X,M,Y):- do(forward).

arrived(X,M,Y):-do(deliver).

submitted([H,P],[M],D) :- do(deliver(H,M,D)).

disconnected :- do(quit).

exception(E,Fc) :- do(deliver(Self,exc(E,Fc),Self)).