Hi all,
Playing around a bit with the test function on the LHS of a rule I
encountered some behavior that puzzles me.
I implemented the following application in which I store facts about
reviews for papers:
(deftemplate review (slot reviewer) (slot paper))
(deffacts MAIN::myfacts
(review (reviewer "1") (paper 1))
(review (reviewer "2") (paper 1))
(review (reviewer "3") (paper 1))
)
I have two rules and one query. The first rule fires for each review.
(defrule rule1
(review (reviewer ?r))
=>
(printout t "rule1 fired for reviewer " ?r crlf)
)
The query evaluates to all reviews per paper and is used in the second
rule that should fire when more than 3 reviews are received for paper 1.
(defquery qry-reviews-for-paper
(declare (variables ?paper))
(review (reviewer ?reviewer) (paper ?paper))
)
(defrule rule2
(test (> (count-query-results qry-reviews-for-paper 1) 3))
=>
(printout t "rule2 fired" crlf)
)
If I run the following code after this specification:
(run)
(assert (review (reviewer "6") (paper 0)))
(printout t "second run" crlf)
(run)
it outputs:
rule1 fired for reviewer 3
rule1 fired for reviewer 2
rule1 fired for reviewer 1
second run
rule1 fired for reviewer 6
I expected the second rule to have fired also, but it didn't. Is it
because the initial-fact is added to the LHS preceding the test and the
rule will only be evaluated once (similar to a rule with an empty LHS)?
This was not clear to me after having read section 6.12 of the manual,
though.
It should also be noted that even if I start with more than three reviews
for paper 1, the second rule only fires if I put the reset command just
before the definition of the rule. I believe the explanation of this
behavior can be found here:
(http://www.mail-archive.com/[email protected]/msg03592.html).
- Nick.
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