Dispatching

Scheduling Logic

Assign Orders


Asprova APS's scheduling process basically consists of repeating over and over again the act of "choosing an operation and assigning it". The procedure that decides the order in which the operations are chosen is called dispatching. As Asprova APS performs a mixture of forward / backward scheduling, the dispatching order does not generally correspond to the order of the operations on the time series.

The "assign orders" command can assign fixed operations. Operations whose times have been fixed are not dispatched but assigned ahead of the ordinary operations, since they must be assigned to the specified times. Other operations are assigned according to the dispatching order.

The dispatching order among these operations is determined according to the settings of the dispatching rule property of the scheduling parameter command. The sort keys specified here determine the dispatching order. This dispatching order, however, is applied only in as much as it does not produce inconsistencies with the constraints on the precedence order of operations in the direction of assignment.

Let us consider the example brought up in the "Explode Orders" section, where the priority and the due date are specified in the order table as below:

[Order Table]
CodeItemOrder quantityPriorityDue dateUser specified assignment direction
L1I11100952003/10/4 17:00:00Forward
L2I11200602003/10/10 14:30:00Backward
L3I21200402003/10/10 14:30:00Forward
L4I21300602003/10/5 14:30:00Backward

If the dispatching rule is specified as

1st keyOrder PriorityDescending
2nd keyOrder due dateAscending

then the dispatching order will be as follows. (Let's assume here that the assignment direction has been determined according to the order priority.)

In this example, the dispatching rule determines only the dispatching order of the orders, while the dispatching order of the operations within a given order is determined according to whether the assignment direction of the order is forward or backward. (starting from the side of first process in case of 'forward,' and from the last process in case of 'backward.') Also note that while orders L3 and L4 correspond to merging processes with two branches, the choice of order between the two branches is arbitrary and is not uniquely defined.

Also, the pegged order is influenced by the order of order conditions in the direction of assignment. For example, suppose that there are Order 1 and Order 2 as shown below and that the dispatching rule is applied in the "descending order of the order priority". When 2 orders are not pegged, the Order 2 becomes ahead in the dispatching order. Please note, however, that in this example, 2 orders are pegged as 1 & 2. According to the "Assignment Direction Deciding Phase", the assignment direction is defined 'forward'. This means that the dispatching order becomes opposite of the dispatching rule and starts from the order 1 from the first manufacturing process.

In cases where there is a results operation, frozen operation, or fixed operation in the order, the dispatching order of operations in this order is defined just as the assignment direction was defined in the assignment direction determination phase.

Also, although in the example above the dispatching rule depended only on the order data and consequently only defined the ordering among the orders (i.e., L1/L4/L2/L3), if the dispatching rules use keys such as "remaining production time" which depend on individual operation information, the dispatching rules will specify an ordering among the operations themselves. In this case, the ordering between the branches of a merging process will also be uniquely defined.



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