JESS: [EXTERNAL] question on sorting

Hi,

I need to rank a set of facts based on a score. I came up with the idea
that I first find the top ranked fact using one rule, followed by ranking
the remaining facts using another rule.

It works. But I suspect that this method will not be very efficient if I
have to rank thousands of facts, rather than just 4 as in my example below.
I also suspect that someone must have solved this sorting problem in a much
better way.

Any recommendation would be much appreciated. Many thanks.

Felix



/******************************************************************/

(deftemplate driver (slot driverId) (slot score) (slot rank))

(defrule rankFirstDriver
    "find top ranked driver if none has been ranked"
    (not (driver (rank ~nil)))               ; if no drivers have been
ranked
    ?d1 <- (driver (score ?s1))              ; if we can find a driver with
score s1
    (not (driver (score ?s2&:(> ?s2 ?s1))))  ; but no other drivers have a
score higher than s1
    =>
    (modify ?d1 (rank 1))
    )

(defrule rankOtherDrivers
    "rank other drivers after top ranked drivers have been found"
    (driver (rank 1)) ; if top ranked driver has been found

    ; find lowest ranked driver
    (driver (rank ?r1&~nil))
    (not (driver (rank ?r2&~nil&:(> ?r2 ?r1))))

    ; find unranked driver with highest score
    ?d <- (driver (score ?s1) (rank nil))
    (not (driver (score ?s2&:(> ?s2 ?s1)) (rank nil)))

    =>
    (modify ?d (rank (+ ?r1 1)))
    )

(reset)
(assert (driver (driverId 1) (score 100)))
(assert (driver (driverId 2) (score 50)))
(assert (driver (driverId 3) (score 200)))
(assert (driver (driverId 4) (score 75)))

(run)
(facts)



/*********************************/

/***** OUTPUT **************/


f-0   (MAIN::initial-fact)
f-1   (MAIN::driver (driverId 1) (score 100) (rank 2))
f-2   (MAIN::driver (driverId 2) (score 50) (rank 4))
f-3   (MAIN::driver (driverId 3) (score 200) (rank 1))
f-4   (MAIN::driver (driverId 4) (score 75) (rank 3))
For a total of 5 facts in module MAIN.