father(abraham,isaac).			male(isaac).
	father(haran,lot).			male(lot).
	father(haran,milcah).			female(milcah).
	father(haran,yiscah).			female(yiscah).

	son(X,Y) :- father(Y,X), male(X).
	daughter(X,Y) :- father(Y,X), female(X).

%	Program 1.2: Biblical family relationships