Remember that pattern-matching is driven by fact assertions,
retractions, and modifications. Matches involving global variables
will be evaluated when working memory changes cause the patterns to
be matched. Changing a global variable will *not* cause the matching
to be reevaluated. So, for example, if you have the following facts:
(deffacts facts
(f 1)
(f 2)
(f 3))
and this variable
(set-reset-globals FALSE)
(defglobal ?*g* = 0)
and this rule
(defrule my-rule
(f ?*g*)
=>
(printout t "Found a match" crlf))
and you say
(reset)
(run)
Then this rule won't fire, of course. But if you then say
(bind ?*g* 1)
(run)
it *still* won't fire, and I suspect that's what's happening to you
here. Changing the global variable doesn't reevaluate the matches;
they were done when the rule was first defined.
BUT... if you say
(reset)
(run)
the rule *will* fire, since reset will remove and replace the facts,
and this time the matches will be evaluated with the new value of ?*g* .
On Nov 27, 2007, at 4:09 PM, A.I. Mannette-Wright wrote:
Hi!
I am a relatively new Jess user so please forgive me
if this question is trivial.
I am running Protege 3.2.1 using JessTab under which I
am running Jess V7.0p1. I have an ontology built in
Protege which I map to Jess facts using the mapclass
function in JessTab. I wrote a rule which uses a
global variable. However the value of the global
variable seems to unknown to the rule. Am I correct
that Jess rules are unaware of the values of variables
that are known to the rest of the Jess environment?
NOte: when I use the printout function I get a valaue
for the variable. Any help would be appreciated.
Thanks..........Anne
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Sandia National Labs FAX: (925) 294-2234
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