Exercise 4.56

Read Exercise 4.56 ~ Solution

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part a

(run-query '(and (supervisor ?name (Bitdiddle Ben))
                 (address ?name ?address)))

(and (supervisor (Tweakit Lem E) (Bitdiddle Ben)) 
     (address (Tweakit Lem E) (Boston (Bay State Road) 22)))
(and (supervisor (Fect Cy D) (Bitdiddle Ben)) 
     (address (Fect Cy D) (Cambridge (Ames Street) 3)))
(and (supervisor (Hacker Alyssa P) (Bitdiddle Ben)) 
     (address (Hacker Alyssa P) (Cambridge (Mass Ave) 78)))

part b

(run-query '(and (salary (Bitdiddle Ben) ?ben-salary)
                 (salary ?name ?salary)
                 (lisp-value < ?salary ?ben-salary)))

(and (salary (Bitdiddle Ben) 60000) 
     (salary (Aull DeWitt) 25000) 
     (lisp-value < 25000 60000))
(and (salary (Bitdiddle Ben) 60000) 
     (salary (Cratchet Robert) 18000) 
     (lisp-value < 18000 60000))
(and (salary (Bitdiddle Ben) 60000) 
     (salary (Reasoner Louis) 30000) 
     (lisp-value < 30000 60000))
(and (salary (Bitdiddle Ben) 60000) 
     (salary (Tweakit Lem E) 25000) 
     (lisp-value < 25000 60000))
(and (salary (Bitdiddle Ben) 60000) 
     (salary (Fect Cy D) 35000) 
     (lisp-value < 35000 60000))
(and (salary (Bitdiddle Ben) 60000)
     (salary (Hacker Alyssa P) 40000) 
     (lisp-value < 40000 60000))

part c

(run-query '(and (supervisor ?name ?supervisor)
                 (job ?supervisor ?supervisor-job)
                 (not (job ?supervisor (computer . ?title)))))

(and (supervisor (Aull DeWitt) (Warbucks Oliver)) 
     (job (Warbucks Oliver) (administration big wheel)) 
     (not (job (Warbucks Oliver) (computer . ?title))))
(and (supervisor (Cratchet Robert) (Scrooge Eben)) 
     (job (Scrooge Eben) (accounting chief accountant)) 
     (not (job (Scrooge Eben) (computer . ?title))))
(and (supervisor (Scrooge Eben) (Warbucks Oliver)) 
     (job (Warbucks Oliver) (administration big wheel)) 
     (not (job (Warbucks Oliver) (computer . ?title))))
(and (supervisor (Bitdiddle Ben) (Warbucks Oliver)) 
     (job (Warbucks Oliver) (administration big wheel)) 
     (not (job (Warbucks Oliver) (computer . ?title))))

At first I thought the ?title in the result was a mistake, but it’s valid and represents a variable – the only way to get rid of it would be to have duplicate answers for each of the possible values for ?title – much like a result set with an SQL inner join.