%‚S”NR‘g TS ???????? : modified by HY

%rule
:-unknown(P,fail).

%23
is_concluded(contract(A,B,C),T3):-
	become_effective(acceptance(B,A,offer(A,B,C)),T3),
	become_effective(offer(A,B,C),T).


%15(1)

become_effective(offer(A,B,C),T1):-
	reach(offer(A,B,C),B,T1),
        \+(become_effective(withdrawl(A,B,offer(A,B,C)),T2)).


%15(2)
become_effective(withdrawl(A,B,offer(A,B,C)),T2):-
        reach(withdrawl(A,B,offer(A,B,C)),B,T2),
        \+((reach(offer(A,B,C),B,T1),T1@<T2)).

%16(1)
become_effective(revocation(A,B,offer(A,B,C)),T2):-
        reach(revocation(A,B,offer(A,B,C)),B,T2),
        \+((dispatch(acceptance(B,A,offer(A,B,C)),A,T1),T1@=<T2)).

become_null(offer(A,B,C),T):-
	become_effective(revocation(A,B,offer(A,B,C)),T).	

%18(2)
become_effective(acceptance(B,A,offer(A,B,C)),T3):-
	reach(acceptance(B,A,offer(A,B,C)),A,T3),
	\+((become_null(offer(A,B,C),T),T@=<T3)).

%fact

/*
%case3c
reach(withdrawl(anzai,bernard,offer(anzai,bernard,sale(agriculture_machine,'$50000'))),bernard,t0407).
reach(offer(anzai,bernard,sale(agriculture_machine,'$50000')),bernard,t0408).
reach(acceptance(bernard,anzai,offer(anzai,bernard,sale(agriculture_machine,'$50000'))),anzai,t0409).
*/

%case3d
% reach(withdrawl(anzai,bernard,offer(anzai,bernard,sale(agriculture_machine,'$50000'))),bernard,t0409).
reach(revocation(anzai,bernard,offer(anzai,bernard,sale(agriculture_machine,'$50000'))),bernard,t0409).
reach(offer(anzai,bernard,sale(agriculture_machine,'$50000')),bernard,t0408).
reach(acceptance(bernard,anzai,offer(anzai,bernard,sale(agriculture_machine,'$50000'))),anzai,t0410).
dispatch(acceptance(bernard,anzai,offer(anzai,bernard,sale(agriculture_machine,'$50000'))),anzai,t0410).