7:25 a.m.
Hi Edson,
Thanks for your help. I restructured my biz objects to avoid nested
structures, which makes it work now (I have new objects to hold
allocatedHour per subject).
However, I have the feeling that this constraint has a certain impact on
o-o design (more flat objects vs composite object). The documentation
says that nested values should be considered immutable, unless using the
modify block (as you suggested) and retract/re-assert the objects in the
workingMemory ; it also has a much greater performance cost.
Am I getting it right when saying that the object design should really
be like 'many flat-type objects avoiding composite approach' to have
Drools perform well or is it more sensible to have a proper o-o design
and tweak Drools (using modify block, disabling cache, etc.)
Thanks in advance for sharing your experience
Regis
when
$lesson : Lesson(allocated == false, session.type == Session.DISTINCT)
$subjectAllocation : SubjectAllocation( subject == $lesson.subject,
$allocatedDays : allocatedDays )
$availableHour : Hour(allocated == false, day not memberOf
$allocatedDays)
then
$lesson.setHour($availableHour ) ;
$lesson.setAllocated(true ) ;
update($lesson) ;
$availableHour.setSubject($lesson.getSubject() ) ;
$availableHour.setAllocated(true ) ;
update($availableHour) ;
$subjectAllocation.addAllocation($availableHour ) ;
update($subjectAllocation) ;
________________________________
From: rules-users-bounces(a)lists.jboss.org
[mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Edson Tirelli
Sent: Monday, April 14, 2008 4:55 PM
To: Rules Users List
Subject: Re: [rules-users] newbie: update and shallowCache
Regis,
You are probably having problems with mutable predicates, when using
"subject.allocatedDays". As a first step to understand your problem, I
strongly encourage you to make constraints flat, i.e., avoid using
nested accessors. After you get used to what can and what can't be done,
you can go back to use nested accessors.
Also, I suggest you use modify() block instead of update():
rule
"allocate"
when
$lesson : Lesson(allocated == false, session.type == Session.DISTINCT )
$subject : Subject( $allocatedDays : allocatedDays ) from
$lesson.subject
$availableHour : Hour(allocated == false, day not memberOf
$allocatedDays)
then
modify( $lesson) {
setHour($availableHour ),
setAllocated(true)
}
modify( $availableHour )
setSubject($lesson.getSubject()),
setAllocated(true )
}
end
Hope it helps.
[]s
Edson
2008/4/14 Piccand, Regis <rpiccand(a)verisign.com>:
Hi all,
I am evaluating Drools and am stuck with a simple rule that
selects elements which do not correspond to the condition... Since I am
updating objects in the RHD, I guess it has to do with my wrong
understanding (and the cache...?)
I am trying to allocate lessons to periods (hour). My object
model can be summarize is as follows :
Lesson
boolean : allocated // true if the lesson has been
allocated to an hour
int : session // a session is a bunch of lessons
Subject : subject // an allocated lesson is assigned a
subject
Subject
Set<Day> : allocatedDays // days in which this subject is
taught - checked before allocation, as a subject can only be taught once
a day
Hour
boolean : allocated // true is this hour has been allocated
with a lesson
Day : day // the day this hour belongs to - required to
check with subject.allocatedDays
I put in the workingMemory a bunch of Lesson objects, which have
been set with Subject and Session id. I also put a bunch of Hour object,
set with a Day.
My rule is as follows:
rule
"allocate"
when
$lesson : Lesson(allocated == false, session.type ==
Session.DISTINCT, $allocatedDays : subject.allocatedDays)
$availableHour : Hour(allocated == false, day not memberOf
$allocatedDays)
then
$lesson.setHour($availableHour ) ;
$lesson.setAllocated(true) ;
update($lesson);
$availableHour.setSubject($lesson.getSubject()) ;
$availableHour.setAllocated(true );
update($availableHour);
end
When I set a debug on the first line of the THEN section, I can
see that sometimes $availableHour.allocated == true ... sometimes
$lesson.allocated == true (although it's an implicit And statement ...)
Therefore, I can see that the update() works, but it seems that
the rule does not use the updated object (due to shallow copy ??)
Any help more than welcome
Regis
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Edson Tirelli
JBoss Drools Core Development
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