% mpjtest.pl -- test file for MPJ.

parent(adam,able) if true.
parent(adam,cain) if true.
parent(eve,able) if true.
parent(eve,cain) if true.
male(adam) if true.
female(eve) if true.
father(X,Y) if parent(X,Y) and male(X).
mother(X,Y) if parent(X,Y) and female(X).
sibling(X,Y) if
  father(Pa,X) and
  father(Pa,Y) and
  mother(Ma,X) and
  mother(Ma,Y) and
  ~(X=Y).