[rules-users] Hard constraints to enforce employee seniority

[Geoffrey De Smet]

Op 08-12-11 23:35, Patrik Dufresne schreef:
> Thanks Geoffrey,
>
> I really like you're suggestion to use intermediate facts to keep the 
> employee's seniority. After this email, I will try to implement it, 
> but I do have a question about your way to implement it. Since my goal 
> is to make senior employee ($higherRankedEmployee) work before a less 
> senior employee ($lowerRankedEmployee), I think the rule should 
> contain a 'not' or a 'not exists' expression. It may be stated as 
> follow :
Yep a "not" is missing, apparently my hands didn't type what my brains 
were thinking :)
"not exists" is not possible (or doesn't make sense), because it's the 
same as just "not" afaik.
>
> rule "hard-Seniority"
> when
>          EmployeeRanking($higherRankedEmployee, $lowerRankedEmployee, 
> $numberOfEmployeesInRankBetweenThem)
>          PlanifEventAssignment(employee == $lowerRankedEmployee)
>          not PlanifEventAssignment(employee == $higherRankedEmployee)
> then
> insertLogical(new IntConstraintOccurrence("hard-Seniority",
> ConstraintType.NEGATIVE_HARD,
> $numberOfEmployeesInRankBetweenThem,
> $employee, $assignment));
> end
>
> Thanks
>
> 2011/12/8 Geoffrey De Smet <ge0ffrey.spam at gmail.com 
> <mailto:ge0ffrey.spam at gmail.com>>
>
>
>
>     Op 07-12-11 21:41, Patrik Dufresne schreef:
>>     Hi all,
>>
>>     I'm trying to create rules to model my problem. So far, I didn't
>>     manage to create rules to make Drools converge to a solution
>>     because of score traps. I don't see any way to avoid it (as I'm
>>     not an expert with Drools). I can express the rule as follow : a
>>     senior employee should work before a less senior employee.
>>
>>     I've implement it as a hard constraint :
>>     rule "hard-Seniority"
>>     when
>>     $employee : Employee()
>>     $assignment : PlanifEventAssignment( $planifEmployee : employee )
>     What's does this $planifEmployee do?
>
>>     not PlanifEventAssignment( employee == $employee )
>>     eval(Helper.compareEmployee($employee, $planifEmployee) < 0)
>>     then
>>     insertLogical(new IntConstraintOccurrence("hard-Seniority",
>>     ConstraintType.NEGATIVE_HARD,
>>     1,
>>     $employee, $assignment));
>>     end
>>
>>     The function Helper.compareEmployee(e1, e2) return -1 if e1 is
>>     more senior then e2 (mostly based on hire date and other boolean
>>     fields).
>>
>     On first sight, in Solution.getProblemFact() I would add these
>     cached problem facts, for any 2 employees (but just once per
>     combination):
>     new EmployeeRanking(higherRankedEmployee, lowerRankedEmployee,
>     numberOfEmployeesInRankBetweenThem)
>
>     then you can do
>     rule "hard-Seniority"
>     when
>              EmployeeRanking($higherRankedEmployee,
>     $lowerRankedEmployee, $numberOfEmployeesInRankBetweenThem)
>              PlanifEventAssignment(employee == $lowerRankedEmployee)
>              PlanifEventAssignment(employee == $higherRankedEmployee)
>
>     then
>     insertLogical(new IntConstraintOccurrence("hard-Seniority",
>     ConstraintType.NEGATIVE_HARD,
>     $numberOfEmployeesInRankBetweenThem,
>     $employee, $assignment));
>
>
>>     This way, the rule make sure a senior employee is working. But
>>     it's a score trap since, many moves are required to resolve the
>>     constraint. e.g:
>>
>>     PlanifEventAssignment1 = e2
>>     PlanifEventAssignment2 = e3
>>     PlanifEventAssignment3 = e4
>>     PlanifEventAssignment4 = e5
>>
>>     e1 is not working. Multiple move are require to reach the best
>>     solution :
>>     PlanifEventAssignment1 = e1
>>     PlanifEventAssignment2 = e2
>>     PlanifEventAssignment3 = e3
>>     PlanifEventAssignment4 = e4
>>
>>     So I'm asking you. What is the best way to make Drools converge ?
>>     Do I need to change my rule, or should I create a BigMove ?
>     course grained moves will work mostly, but solving the score trap
>     itself is a far better long-term solution (and it still allows you
>     to add course grained moves later).
>>
>>     -- 
>>     Patrik Dufresne
>>
>>
>>     _______________________________________________
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>>     rules-users at lists.jboss.org  <mailto:rules-users at lists.jboss.org>
>>     https://lists.jboss.org/mailman/listinfo/rules-users
>
>     -- 
>     With kind regards,
>     Geoffrey De Smet
>
>
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>
>
>
>
> -- 
> Patrik Dufresne
>
>
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-- 
With kind regards,
Geoffrey De Smet

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