Question

我在理解在一个OptaPlanner演示示例（NurseRostering应用程序）中实现的Drools规则时遇到了问题。任何人都可以解释以下规则如何运作：

// a nurse can only work one shift per day, i.e. no two shift can be assigned to the same nurse on a day.
rule "oneShiftPerDay"
when
    $leftAssignment : ShiftAssignment($leftId : id, $employee : employee, $shiftDate : shiftDate)
    $rightAssignment : ShiftAssignment(employee == $employee, shiftDate == $shiftDate, id > $leftId)
then
    insertLogical(new IntConstraintOccurrence("oneShiftPerDay", ConstraintType.NEGATIVE_HARD,
            1,
            $leftAssignment, $rightAssignment));
end

是否有任何资源详细说明规则的解释及其实施方式？当我在网上和一些书中查看一些例子时，我发现它很容易理解，但是当我查看Drools提供的样本时，我无法理解。

Answer 1

when
    // When a specific shift with id $leftId is assigned to employee $employee and that shift is on date $shiftDate
    $leftAssignment : ShiftAssignment($leftId : id, $employee : employee, $shiftDate : shiftDate)
    // AND there is another shift assigned to the same for the same date and with a higher id
    $rightAssignment : ShiftAssignment(employee == $employee, shiftDate == $shiftDate, id > $leftId)
then
    // Then this solution is penalized: it gets -1 hard score point
    scoreHolder.addHardConstraintMatch(kcontext, -1);

注意：在那时，我使用了OptaPlanner 6语法（而不是弃用的Planner 5.x语法），因为它是faster and easier。

关于id < $leftId部分：这是为了确保Drools只将ShiftAssignment A与ShiftAssignment B（给出A-B）而不是A-A，B-B，B-A匹配，以避免过多惩罚。

Answer 2

为了学习DRL的语法，我建议在这里阅读Drools文档：

http://docs.jboss.org/drools/release/6.0.0.CR1/drools-expert-docs/html/ch04.html

根据我的理解，它对OptaPlanner / Drools Planner Docs的规则设置有所帮助。

NurseRostering应用程序中Drools规则的说明

2 个答案: