Database rule help!

[lagg]

i need help with a prolog rule. The database is outlined as follows

is_below(bob,jim).
is_below(jim,dave).
is_below(dave,sam).
is_below(sam,pete).
is_below(pete,colin).
is_below(colin,eric).
is_below(eric,steve).
is_below(steve,paul).
is_below(paul,jack).

It shows the rank people, bob is 1 place lower than Jim etc. I want to write a rule which returns the highest person?
top_person(X)
and also a rule to check if one person is higher than the next
higher(colin,jack).
Can you give me some help please?

 

[2Dittmar]

top_person(X) :-
is_bewlow(_,X),
not(is_below(X,_)).


higher(X,Y) :-
bewlow(Y,X).
higher(X,Y) :-
below(Y,X1),
higher(X,X1).

this of course only works if is_below(X,Y) means that X is below Y, so Y is higher than X. Why do i say this? because u didnt say how to interpret ur fact is_below/2. if its reverse u have to change the predicates i made