CLIPS Clause Interdependence - clips

Question

I'd like to remove two of the test conditional elements from the following rule as well as improve the readability of it.
(defrule compare-things
(logical ?thing0 <- (object (is-a TYPED_THING)
(type-results $? ?t0 $?)))
(logical ?thing1 <- (object (is-a TYPED_THING)
(type-results $? ?t1 $?)))
(thing-comparable ?type)
?type0 <- (object (is-a TYPING)
(qualified-type ?type ?model ?mode ?comp0))
?type1 <- (object (is-a TYPING)
(qualified-type ?type ?model ?mode ?comp1))
; This test exists to restrict the number of rule firings
(test (> (str-compare (instance-name ?thing0) (instance-name ?thing1)) 0))
; Ideally, the following two tests can be removed
(test (= (str-compare (instance-name ?type0) (instance-name ?t0)) 0))
(test (= (str-compare (instance-name ?type1) (instance-name ?t1)) 0))
=>
(make-instance of COMPARISON
(compares ?thing0 ?thing1)
(score nil)
)
(printout t "comparing: " (instance-name ?thing0) (instance-name ?thing1) crlf)
)
The multislot field values ?t0 and ?t1 should correspond to the same instances as ?type0 and ?type1. If I replace ?t0 and ?t1 with ?type0 and ?type1 (which is intuitive first attempt), then I receive the following error while loading the rules:
Defining defrule: compare-things
[ANALYSIS2] Pattern-address ?type0 used in CE #4 was previously bound within a pattern CE.
[ANALYSIS2] Pattern-address ?type1 used in CE #5 was previously bound within a pattern CE.
ERROR:
(defrule MAIN::compare-things
(logical
?thing0 <- (object (is-a TYPED_THING)
(type-results $? ?type0 $?)))
(logical
?thing1 <- (object (is-a TYPED_THING)
(type-results $? ?type1 $?)))
(thing-comparable ?type)
?type0 <- (object (is-a TYPING)
(qualified-type ?type ?model ?mode ?comp0))
?type1 <- (object (is-a TYPING)
(qualified-type ?type ?model ?mode ?comp1))
(test (> (str-compare (instance-name ?thing0) (instance-name ?thing1)) 0))
=>
(make-instance of COMPARISON
(compares ?thing0 ?thing1)
(score nil))
(printout t "comparing: " (instance-name ?thing0) (instance-name ?thing1) crlf))
FALSE
The following data is being used to stimulate the rule in development:
(defclass TYPING (is-a USER)
(role concrete)
(multislot qualified-type (access initialize-only)
(type STRING)
(cardinality 4 4))
(slot score (access initialize-only)
(type FLOAT))
)
(defclass TYPED_THING (is-a USER)
(slot id (access initialize-only)
(type INTEGER))
(multislot type-results (access initialize-only)
(type INSTANCE)) ; of TYPING
)
(defclass COMPARISON (is-a USER)
(multislot compares (access initialize-only)
(type INSTANCE) ; of TYPED_THING
(cardinality 2 2))
(slot score (access read-write)
(type FLOAT))
)
; These facts tag top-level types that are comparable
(deffacts KNOWN_COMPARABLE_TYPES
(thing-comparable "cat-a")
(thing-comparable "cat-c")
)
(definstances KNOWN_THINGS
(thing0 of TYPED_THING
(id 0)
(type-results (make-instance of TYPING (qualified-type "cat-a" "x0" "y0" "z0")(score 0.9))
(make-instance of TYPING (qualified-type "cat-b" "x0" "y0" "z0")(score 0.9))))
(thing1 of TYPED_THING
(id 1)
(type-results (make-instance of TYPING (qualified-type "cat-a" "x0" "y0" "z1")(score 0.9))
(make-instance of TYPING (qualified-type "cat-a" "x1" "y1" "z0")(score 0.9))))
(thing2 of TYPED_THING
(id 2)
(type-results (make-instance of TYPING (qualified-type "cat-b" "x0" "y0" "z1")(score 0.9))))
)
Which should produce the following output (as it currently does):
CLIPS> (reset)
CLIPS> (run)
comparing: [thing1][thing0]

Answer 1

Working within the limitation indicated by the error message, you can get the rule to compile with this modification:
(defrule compare-things
(logical ?thing0 <- (object (is-a TYPED_THING)
(type-results $? ?t0 $?)))
(logical ?thing1 <- (object (is-a TYPED_THING)
(type-results $? ?t1 $?)))
(thing-comparable ?type)
(object (is-a TYPING)
(name =(instance-name ?t0))
(qualified-type ?type ?model ?mode ?comp0))
(object (is-a TYPING)
(name =(instance-name ?t1))
(qualified-type ?type ?model ?mode ?comp1))
; This test exists to restrict the number of rule firings
(test (> (str-compare (instance-name ?thing0) (instance-name ?thing1)) 0))
=>
(make-instance of COMPARISON
(compares ?thing0 ?thing1)
(score nil)
)
(printout t "comparing: " (instance-name ?thing0) (instance-name ?thing1) crlf)
)