#const n=6.      

%%%%%%%%%%%%%%%%%%%%  SCENARIO 2 %%%%%%%%%%%%%%%%%%
%                                                 %
%     John took the plane from Paris to Baghdad.  %
%     On the way the plane stopped in Rome.       %
%     Is John in Baghdad?                         %
%                                                 %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%           THE TRANSLATION

% Statement 1 and the query as before. 
% Statement 2 is new.

%     John took the plane from Paris to Baghdad. 

            h(at(john,paris),0).
            o(go_on(john,j(paris,baghdad)),0).

%     On the way the plane stopped in Rome. 

            o(stop(j(paris,baghdad),rome),2).

%  The query:

answer_true(q) :-
	h(at(john,baghdad),n).
answer_false(q) :-
	-h(at(john,baghdad),n).
type_query(q,boolean).   

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%  The difficulty with the translation of 
%  statement 2 is in figuring out that "stopping 
%  in Rome" happened between departure from Paris
%  and arrival in Baghdad. But even if this is done
%  we need to determine the exact "step" when
%  it occurs (in our case, 2). 

%  One possible way to find this value is to 
%  translate the first sentence and run 
%  the program with n=1,2,... as before.
%  With n=4 you'll obtain:

%  do(embark(john,j(paris,baghdad)),0)
%  do(depart(j(paris,baghdad)),1)
%  do(stop(j(paris,baghdad),baghdad),2)
%  do(disembark(john,j(paris,baghdad)),3)

% This information can be useful in determining
% that stopping in Rome happened at step 2.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% As before we'll run the program together with
% the rules and directives below.

       yes :- 
           type_query(Q,boolean),
           answer_true(Q).

       no :- 
           type_query(Q,boolean),
           answer_false(Q).

       maybe :- 
           type_query(Q,boolean),
           not yes, 
           not no.

hide.

show yes,no,maybe,do(A,B).