You may want to also try attaching a salience attribute to each rule.
-----Original Message-----
From: Michael Neale [mailto:[EMAIL PROTECTED]
Sent: Friday, 27 January 2006 11:06 AM
To: user@drools.codehaus.org
Subject: Re: [drools-user] Scheduling/Timetabling with drools
No I don't think you need to follow miss manners. Miss manners is designed
to stress rule engines for performance profiling reasons, so probably not
ideal to emulate !
I am not quite across what you are doing, but I can take a wild stab... (I
hope no one gets hurt)...
Well in the first rule when you match a Task to a Slot and then modify,
instead assert a new object which is a tuple of the Task and Slot
combination. Then have a 2nd rule which checks that combination - if its
bad, it retracts that combination. If its OK, then it does the assignment
(if it wasn't done before), and then retracts those Tasks/Slots so they are
not considered again. Can something like that work? Or did I just take out
someone eye (I can hear the screaming).
Michael.
On 1/27/06, Robert Jaemmrich <[EMAIL PROTECTED]> wrote:
>
> Hi,
>
> is it possible (or wise ;-) to use drools in a scheduling application?
>
> I want to place Tasks into Timeslots. Placement is dependant on certain
> constraints (hard or maybe soft) and ressources. Each slot can contain
> one task.
>
> E.g. I have some tasks {t1,t2,t3} to place on slots {s1,s2,s3,s4}.
>
> Constraints are defining which slots a task may be placed into
> (c1{t1;s1..s4}, c2{t2;s1,s4}) or define a task sequence
> (task1.slotNumber < task2.slotNumber).
>
> My naive "newbie approach" is to define two rules like this:
>
> <rule name="Assign Next" no-loop="yes">
> <parameter identifier="task">
> <class>Task</class>
> </parameter>
> <parameter identifier="slot">
> <class>Slot</class>
> </parameter>
> <java:condition>
> slot.getTask() == null
> </java:condition>
> <java:condition>
> task.getSlot() == null
> </java:condition>
> <java:consequence>
> System.out.println("Placing "+task.getName()+" on
> "+slot.getName());
> task.setSlot(slot);
> slot.setTask(task);
> drools.modifyObject(slot);
> drools.modifyObject(task);
> </java:consequence>
> </rule>
>
> <rule name="Reset">
> <parameter identifier="task">
> <class>Task</class>
> </parameter>
> <parameter identifier="constraint">
> <class>Constraint</class>
> </parameter>
> <java:condition>
> task.getSlot() != null
> </java:condition>
> <java:condition>
> !constraint.isOK(task)
> </java:condition>
> <java:consequence>
> System.out.println("Resetting ... ");
> Slot slot = task.getSlot();
> task.setSlot(null);
> drools.modifyObject(task);
> slot.setTask(null);
> drools.modifyObject(slot);
> </java:consequence>
> </rule>
>
> It assigns tuples of "Slot" and "Task" first and checks if they are ok
> (constraint.isOK) second. This leads to an infinite loop flipping
> between the two rules.
>
> Do I have to use a more "Miss Manners"ish approach of implementing some
> sort of backtracking mechanism by myself? I think I have to use some
> kind of depth search to avoid wasting huge quantities of workingMemory ..?
>
> Any help would be appreaciated! ;-)
>
>
> TIA,
>
> Robert
>
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