Hi Dr. Friedman-Hill,
I ran into a bug in my rulebase today that I traced back to the use of
the no-loop declaration (test case below). This has bit other users in
the past (see urls below), and I think it should be regarded as a bug.
In my example, two separate facts (f-2 and f-3) activate a no-loop
rule. When the rule fires for f-3, it modifies (retracts and reasserts)
another fact, causing the activation associated with f-2 to be removed.
However, when the fact is reasserted, 'no-loop' prevents the engine from
restoring the activation for f-2.
This behavior seems inconsistent with the definition of the no-loop
declaration. The RHS of a 'no-loop' rule must not *cause* the immediate
reactivation of the same rule, but it should not inhibit an activation
that was already present when the rule fired.
Thanks,
~~Aaron Novstrup
http://www.mail-archive.com/[email protected]/msg08025.html
http://www.mail-archive.com/[email protected]/msg09870.html
; JESS test case
(deftemplate box
(multislot items))
(deffunction put-in-box (?box ?item)
(bind ?items (fact-slot-value ?box items))
(modify ?box (items (union$ ?items (create$ ?item))))
)
(defrule box-packer-rule
(declare (no-loop TRUE))
(moving ?item)
?b <- (box)
=>
(put-in-box ?b ?item)
)
(watch all)
(reset)
(assert (box))
(assert (moving elvis-bobble-head-collection))
(assert (moving jimi-hendrix-autographed-guitar))
(run)
; execution trace
Jess, the Rule Engine for the Java Platform
Copyright (C) 2008 Sandia Corporation
Jess Version 7.1p2 11/5/2008
==> Focus MAIN
==> f-0 (MAIN::initial-fact)
==> f-1 (MAIN::box (items ))
==> f-2 (MAIN::moving elvis-bobble-head-collection)
==> Activation: MAIN::box-packer-rule : f-2, f-1
==> f-3 (MAIN::moving jimi-hendrix-autographed-guitar)
==> Activation: MAIN::box-packer-rule : f-3, f-1
FIRE 1 MAIN::box-packer-rule f-3, f-1
<== Activation: MAIN::box-packer-rule : f-2, f-1
<=> f-1 (MAIN::box (items jimi-hendrix-autographed-guitar))
<== Focus MAIN
begin:vcard
fn:Aaron Novstrup
n:Novstrup;Aaron
org:Stottler Henke Associates Inc.
adr;dom:;;1107 NE 45th St;Seattle;WA;98105
email;internet:[email protected]
title:AI Software Engineer
tel;work:206.545.2941
tel;cell:805.701.9786
x-mozilla-html:FALSE
url:www.stottlerhenke.com
version:2.1
end:vcard
