•s
•step:
•goal:
•child(2$_$_1?Y,2$_$_1?Z)./2
•goallist:
•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,christine)(2$_$_1?Y,elza)]
•
•history:
•(child(christine,elza)./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)
•