Exercise 4.58

Posted on by Barry Allison

Read Exercise 4.58 ~ Solution

My first attempt was to find a boss who is in another division…

(run-query 
 '(assert! 
   (rule (big-shot ?name ?division)
         (and (job ?name (?division . ?title))
              (supervisor ?name ?boss)
              (job ?boss (?division-2 . ?title-2))
              (not (same ?division ?division-2))))))

(run-query '(big-shot ?who ?where))
(big-shot (Scrooge Eben) accounting)
(big-shot (Bitdiddle Ben) computer)

.. but as pointed out by John Donnellan in the comments, that’s not right because some people do not have a supervisor. We need people who

  • don’t have a supervisor OR
  • have a supervisor in a different division.

Second attempt:

(run-query
 '(assert!
   (rule (big-shot ?name ?division)
         (and (job ?name (?division . ?title))
              (or (not (supervisor ?name ?boss))
                  (and (supervisor ?name ?boss)
                       (not (job ?boss (?division . ?title-2)))))))))

(run-query '(big-shot ?who ?where))
(big-shot (Warbucks Oliver) administration)
(big-shot (Scrooge Eben) accounting)
(big-shot (Bitdiddle Ben) computer)

2 thoughts on “Exercise 4.58”

  1. Hi thanks again for your blog. I think Oliver Warbucks may be missing from the results. He is in the Adminstration division, but he does not have a supervisor in Adminstration division. I think the query above is asking “Who has an boss in a different division?” (which doesn’t include Oliver), whereas “Who does not (have a boss in same division)?” does include Oliver.

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