(male avraham)
(female sara)
(parent avraham yzhak)
(parent sara yzhak)
(all (?x) (<=> (female ?x) (not (male ?x))))
(all (?x ?y) (=> (and (parent ?x ?y)  (male ?x)) (father ?x ?y)))
(all (?x ?y) (=> (father ?x ?y)  (and (parent ?x ?y) (male ?x))))
(all (?x ?y) (=> (and (parent ?x ?y)  (not (father ?x ?y))) (mother ?x ?y)))
(all (?x)  (exi (?y) (=> (mother ?x ?y) (female ?x))))