NurseRostering應用程序中Drools規則的說明

Question

我在理解在OptaPlanner演示示例（NurseRostering應用程序）之一中實現的Drools規則時遇到問題。誰能解釋下面的規則是如何工作的：

// 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 

是否有大約規則的解釋和方式詳細其中規定任何資源得到實施？當我在網上和某些書中查看一些示例時，我發現它很容易理解，但是當我檢查Drools中提供的示例時，我無法得到一個想法。

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：在隨後的一面，我用了OptaPlanner 6語法（而不是過時的計劃5.x的語法），因爲它是faster and easier。

關於id < $leftId部分：爲了確保Drools只與ShiftAssignment A和ShiftAssignment B匹配（它給出了A-B）而不是A-A，B-B和B-A，以避免懲罰太多。

Answer 2

爲了學習DRL的語法的緣故，我建議在這裏閱讀的Drools文檔：

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

對於我的理解它比OptaPlanner/Drools的規劃師文檔多一點幫助了我關於規則設置。