s
step:
goal:
/0
goallist:
/0
child(2$_$_1?Y,2$_$_1?Z)./2
gender(1$_$_2?Z,female)./2
substitution:
[(_1?Z,1$_$_2?Z)(_1?X,1$_$_2?X)(1$_$_2?Z,2$_$_1?Z)(1$_$_2?X,2$_$_1?X)(2$_$_1?X,wim)(2$_$_1?Y,christine)]
history:
(child(wim,christine)./2,child(2$_$_1?X,2$_$_1?Y)./2)
(child(2$_$_1?X,2$_$_1?Y),child(2$_$_1?Y,2$_$_1?Z) :>
grandparent(2$_$_1?Z,2$_$_1?X)./2,grandparent(1$_$_2?Z,1$_$_2?X)./2)
(grandparent(1$_$_2?Z,1$_$_2?X),gender(1$_$_2?Z,female)
:> grandmother(1$_$_2?Z,1$_$_2?X)./2,grandmother(_1?Z,_1?X)./10)