Exercise 4.69.  Beginning with the data base and the rules you 
formulated in exercise 4.63, devise a rule for adding ``greats'' to a 
grandson relationship. This should enable the system to deduce that Irad 
is the great-grandson of Adam, or that Jabal and Jubal are the 
great-great-great-great-great-grandsons of Adam. (Hint: Represent the 
fact about Irad, for example, as ((great grandson) Adam Irad). Write 
rules that determine if a list ends in the word grandson. Use this to 
express a rule that allows one to derive the relationship ((great . 
?rel) ?x ?y), where ?rel is a list ending in grandson.) Check your rules 
on queries such as ((great grandson) ?g ?ggs) and (?relationship Adam 
Irad).

————————————————————————————————————————————————————————————————————————

data:

(son Adam Cain)
(son Cain Enoch)
(son Enoch Irad)
(son Irad Mehujael)
(son Mehujael Methushael)
(son Methushael Lamech)
(wife Lamech Ada)
(son Ada Jabal)
(son Ada Jubal)

(rule (ends-in-gs (grandson)))

(rule (ends-in-gs (?a . ?b)) (ends-in-gs ?b))

(rule ((great grandson) ?a ?b)
  (and (son ?a ?c)
       (grandson ?c ?b)))

(rule ((great . ?rel) ?a ?b)
  (and (ends-in-gs ?rel)
       (son ?a ?c)
       (?rel ?c ?b)))