E.1 OPS5

OPS5 rulebases may be readily converted into KnowledgeWorks rulebases. The main OPS5 forms needing conversion are:

• literalize into def-kb-struct or def-kb-class. For example:

  (literalize employee name father-name mother-name)
  

  could become:

  (def-kb-struct employee name father-name mother-name)
  

• strategy into a defcontext form with the right conflict resolution strategy. For example:

  (strategy lex)
  

  could become:

  (defcontext ops5 :strategy (lex specificity))
  

  and:

  (strategy mea)
  

  could become:

  (defcontext ops5 :strategy (mea lex specificity))
  

In OPS5 you cannot have different conflict resolution strategies for different sets of rules. The KnowledgeWorks context mechanism for passing control is much clearer and more powerful than, for instance, the use of the MEA strategy as sole control mechanism in OPS5.

• p into defrule. For example, the OPS5 rule:

  (p recognize-pair
    (employee ^name <parent>)
    (employee ^name <child> ^mother-name <parent>)
    -->
    (make pair))
  

  will become:

  (defrule recognize-pair :forward
    (employee ? name ?parent)
    (employee ? name ?child mother-name ?parent)
    -->
    (assert (pair ?)))
  

As an extended example below are given some OPS5 rules from the Monkey and Banana problem (see Appendix B: Examples):

(strategy mea)
(literalize monkey
  name at on holds)
(literalize object
  name at weight on)
(literalize goal
  status type object to)
(literalize start)
 
(p mb1
  (goal ^status active ^type holds ^object <w>)
  (object ^name <w> ^at <p> ^on ceiling)
  -->
  (make goal ^status active ^type move ^object ladder
        ^to <p>))
 
(p mb4
  {(goal ^status active ^type holds ^object <w>) <goal>}
  (object ^name <w> ^at <p> ^on ceiling)
  (object ^name ladder ^at <p>)
  {(monkey ^on ladder ^holds nil) <monkey>}
  -->
  (write (crlf) Grab <w>)
  (modify <goal> ^status satisfied)
  (modify <monkey> ^holds <w>))
 
(p mb8
  (goal ^status active ^type move ^object <o> ^to <p>)
  (object ^name <o> ^weight light ^at <> <p>)
  -->
  (make goal ^status active ^type holds ^object <o>))

In KnowledgeWorks this could be:

(defcontext ops5 :strategy (mea lex specificity))
 
(def-named-kb-class monkey ()
  ((at :initform nil)
   (on :initform nil)
   (holds :initform nil)))
 
(def-named-kb-class object ()
  ((at :initform nil)
   (weight :initform nil)
   (on :initform nil)))
 
(def-kb-struct goal status type object to)
(def-kb-struct start)
 
(defrule mb1 :forward
  :context ops5
  (goal ? status active type holds object ?w)
  (object ? name ?w at ?p on ceiling)
  -->
  (assert (goal ? status active type move object ladder
                  to ?p)))
 
(defrule mb4 :forward
  :context ops5
  (goal ?g status active type holds object ?w)
  (object ? name ?w at ?p on ceiling)
  (object ? name ladder at ?p)
  (monkey ?m on ladder holds nil)
  -->
  ((format t "~%Grab ~S" ?w))
  (assert (goal ?g status satisfied))
  (assert (monkey ?m holds ?w)))
 
(defrule mb8 :forward
  :context ops5
  (goal ? status active type move object ?o to ?p)
  (object ? name ?o weight light at ?q)
  (test (not (eq ?q ?p)))
  -->
  (assert (goal ? status active type holds object ?o)))