Queue Modes (Ordering Disciplines)

Selecting a Queue Mode will affect the way that incoming items are ordered into the group of waiting items.

First In First Out

The first item to enter the queue is the first to leave. Items queue behind each other in the order they have arrived. This is the default for a queue.

Last In First Out

Later items leave earliest. The last item to enter the queue is the first to leave. Items entering the queue move in front of existing items in the queue.

Highest Priority First

Higher priority items are put first. (Priority is an attribute ot the item that can be set when editing the item, or altered in a change object routine).

Lowest Priority First

Items entering the queue go in front of other items which have a lower item priority than themselves.
Highest Attribute First
Items with a higher value for a selected Item Attribute are put first.

Lowest Attribute First

Items with a lower value for a selected Item Attribute are put first.

Any Item Can Leave

Used in situations where a regular Item, or Carrier Item may be called upon in no particular order by PickUp objects, or in model logic in combination with Switch Objects.

Send Message

Used when you want to send an Item to another location in your model to be processed. In this Mode you nominate a Target Entry from a list of available Message Entries. The Message Entry nominated need not be in the same subsystem. Refer to <Send Message> for more details.

Send Directed Message

Used when you want to direct a message to a alternative message entries. You get to specify the Target Object in this case using an Attribute, which means the Target may be variable. Refer to <Send Directed Message> for more details.

Directed Message for Carried Items

In this mode a queue will send a message for every item that entering item is carrying. This enables processing of statistics, inspection of carried items etc. to be performed without the overhead of dropping off all the carried items then picking them all up again using DropOff and PickUp Objects. Refer to <Directed Message for Carried Items> for more details.

Send Scoped Broadcast

This mode enables a queue to send a specific broadcast to a hierarchy of subsystems. The top is specified using a portal in the object list. Unlike a change object broadcast, the broadcast is sent immediately, whilst the item waits in the queue. The item only leaves the queue once all listening entries have produced their broadcast items and they have flowed as far as they can before encountering capacity. Refer to <Send Scoped Broadcast> for more details.

Wait For Specific Release

Queues can be set to hold items until there is a message sent to have a specific Item Released. Items entering the queue wait there until the routine operation "Release Item" is used to release them from the queue. The "Release Item" routine operation takes 2 parameters, Item Index and Scope Panel, representing the Item ID System Attribute value, and the Panel from which scope to broadcast the instruction. Refer to Wait for Specific Release for more details.

Restart Engine/Continue

Queues in this mode restart the model engine whilst retaining the item within them. ALL OTHER ITEMS in the model are deleted - the run is stopping and restarting at time = 0, but the item at the queue "survives" the restart and can continue through its flow. Refer to <Restart Engine/Continue> for more details.

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