On 9/28/05, Alan Moore <[EMAIL PROTECTED]> wrote:
> Jerome,
> I'm a little confused as to why your example below would work for either
> set of facts.
Hey Jerome,
Perhaps this generic example will be of some help....
Since you introduced the notion of sets, let's say that we have a set
called A. For sake of argument, we'll add that set A has five
properties. We'll call this set of properties X and we can write
that:
X = {x1, x2, x3, x4, x5}
So, each element of A can be defined by the values of its five
properties. If we represent elements of set A by ordered facts of
type A, then we can write:
(deftemplate A
(slot x1) (slot x2) (slot x3) (slot x4) (slot x5))
Now, let's say that we want to find a subset, B, of all type A facts
having certain property values. Note that we're not creating any new
facts of type B. We are just extracting a subset from the collection
of A facts. To do this, we simply restrict the slot values using
Jess's constraints.
For example, if you asked me to find subset B such that:
x1 < 3
x2 > 2
x3 = x4
x5 = nil
I could write:
(defrule find-subset-B
(A (x1 ?x1&:(< x1 3)) (x2 ?x2&:(> x2 2)) (x3 ?x3) (x4 ?x3) (x5 nil))
=>
; Rule actions go here...
)
This rule would fire on all facts of type A for which these
constraints were satisfied.
A complete program is given below.
Cheers,
-Jason
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;; -------------------------
;; subset.clp
;; -------------------------
; INIT
(clear)
(watch rules)
(deftemplate A
(slot x1) (slot x2) (slot x3) (slot x4) (slot x5))
; Load some data
(deffacts load-all-A-facts
(A (x1 3) (x2 9) (x3 8) (x4 2) (x5 0.4))
(A (x1 -2) (x2 5) (x3 0.3) (x4 0.3) (x5 nil))
(A (x1 1) (x2 3) (x3 7) (x4 5) (x5 8))
(A (x1 3) (x2 5) (x3 9) (x4 1) (x5 nil))
(A (x1 9) (x2 3) (x3 8) (x4 4) (x5 5))
(A (x1 3) (x2 2) (x3 1) (x4 1) (x5 2))
(A (x1 1) (x2 5) (x3 4) (x4 4) (x5 nil))
(A (x1 0) (x2 4) (x3 4) (x4 1) (x5 3)))
; Filter set A for subset B
(defrule find-subset-B
?fact<- (A (x1 ?x1&:(< ?x1 3)) (x2 ?x2&:(> ?x2 2)) (x3 ?x3) (x4
?x3) (x5 nil))
=>
(printout t (fact-id ?fact) " matches!" crlf))
; PROGRAM
(reset)
(run)
; OUTPUT
;Jess, the Rule Engine for the Java Platform
;Copyright (C) 2005 Sandia Corporation
;Jess Version 7.0b2 8/11/2005
;
;FIRE 1 MAIN::find-subset-B f-7
;<Fact-7> matches!
;FIRE 2 MAIN::find-subset-B f-2
;<Fact-2> matches!
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