•s
•step:
•goal:
•grandparent(1$_$_2?Z,1$_$_2?X)./2
•goallist:
•grandparent(1$_$_2?Z,1$_$_2?X)./2
•gender(1$_$_2?Z,female)./2
•
•substitution:
•[(_1?Z,1$_$_2?Z)(_1?X,1$_$_2?X)]
•
•history:
•(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)
•