(in-module "FAMILY")

(defconcept PERSON (?p))
(defconcept MALE (?m) :=> (PERSON ?m))
(defconcept FEMALE (?f) :=> (PERSON ?f))

(defrelation PARENT (?p ?c)
  :documentation "?p is a parent of ?c")

(defrelation FATHER (?f ?c)
  :=> (and (MALE ?f) (PARENT ?f ?c)))

(defrelation MOTHER (?m ?c)
  :=> (and (FEMALE ?m) (PARENT ?m ?c)))

(assert (MALE John))
(assert (FEMALE Mary))
(assert (MALE Tom))
(assert (PARENT John Tom))
(assert (PARENT Mary Tom))

(retrieve all (?f ?c) (FATHER ?f ?c))