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Items, Properties, and Values 133
Item properties
Like attributes, a priority is a type of item property that can be assigned to an item. Priorities signify the impor- tance of items. Using the _Item priority property, you can assign priorities to items and manipulate them based on their priorities.
Setting an item’s priority
Priorities are particularly
useful when you want to
examine a population of
waiting items and deter-
mine their processing order.
For example, you might
have a step in a manufac-
turing process where a worker examines the pending job orders and chooses the one that is the most urgent.
☞ Items can only have one priority. If you need multiple levels of priorities, use attribute values instead.
When a new priority is added to an item that already has a priority, the new priority prevails. When items are batched, the highest priority of the items prevails in the resulting batched item.
☞ The lowest value (including negative values) represents the top priority.
Setting, getting, and using priorities
The following table lists some common priority-based modeling activities and the blocks that are usually used to facilitate them. All blocks are from the Item library.
To Do This:
Initialize newly created items with priorities
Define default priorities for resource items
Set, modify, or check priorities on existing items Select incoming items based on priorities
Sort and release items based on priorities
Sort items based on priority and conditionally release them based on an equation
View an item’s priority
Allocate resource pool units to the highest ranked item first
Use Block(s)
Create (when “Create items by schedule” is the selected behavior)
Resource Item
Set, Get, Equation(I)
Select Item In (when “Select input based on item priority” is chosen)
Queue (when it sorts by priority) Queue Equation
Get, History Resource Pool
Discrete Event

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