Queue

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Queue Icon.jpg

A Queue is an area where Items can wait.

When a number of items want to access an Object all at the same time, and the Object cannot accept them all at the same time, then the items must compete for access.

In real world systems you will often see queues or line-ups forming to facilitate this competing according to various rules.

In Planimate, the Queue Object provides a place for you the modeller to apply rules to manage competition for access to Objects.

Queues can be classified as “Logical with Capacity”.

Queue in a Flow.jpg

Normally, items entering the queue will appear at the end and move down through the queue until they can proceed to their destination. This can be altered by using a different queue discipline. The length, position and orientation of a queue can be changed. The actual maximum capacity can be set separately to the screen size.

Queue States

Queues display differently from the other objects in Planimate®.

They are shown graphically as a line-up of the items waiting in the queue.

However they still have two states.

Empty  No items are waiting in the queue.

Occupied  At least one item occupies the queue.


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.


Queue Capacity and Length

These options enable you to set the size of the queue.

Capacity

Sets the maximum number of items which may be in the queue at a time.

Screen Length

Sets the number of items that are shown on the screen (maximum of 16).

When Capacity exceeds screen length, extra items are not shown but are indicated in a counter.

Setting this value to 0 causes only the counter to be shown.


Queue Direction

This option enables you to determine the direction in which the queue will grow

Left to Right; Right to Left; Up to Down; Down to Up


Queue Options

Queues have two options.

Pause On Overflow

Default: Off

Setting this option means that when the queue reaches its capacity, the model run will be paused, and the screen the queue resides on will be displayed. The item is left in the queue so it can be inspected (if capacity follows the queue the item will move when   the model continues)This is sometimes useful for debugging. Single item queues with this option on can be used to catch unexpected conditions in a run and unlike the exit, they enable the problem item to be examined.

Show Overflow

Default: On

This option displays the overflow box when the number of items in the queue exceeds the screen display length. The box displays the number of extra items not visible.

The full occupancy value of a queue is thus the sum of this overflow figure, and the number of visible items.

If this Option is not selected, the number of Non-Visible items is not displayed.


Position Reneg Exit

This option enables you to send items that depart the queue on the Reneg Path to a different position than the regular exit, so that these departures may be clearly recognised.


Allowing Items to Abandon a Queue

You can configure a queue such that after a period of time waiting in the queue, an Item will leave the queue via an alternative (higher number) path.

In Interaction Mode you can add a queue renegotiation time.

This function provides a limit to the time an object will spend in the queue.

When this time expires the item will exit the queue via a secondary path.

You need to make sure that a second path from the queue exists when you use this feature, or the model will complain when the item tries to abandon the queue and finds no path available to do so.

Reneg Time

Reneg Time is the name given to the time period the item will wait in the queue.

Reneg Time is specified by item class, thus it is an interaction, and you edit this setting in interaction view.

Reneg Time can be varied randomly if a distribution pattern is used.

The Reneg Time may be - or be scaled by - an Item or Portal Attribute.

Using an Item Attribute for this purpose permits different items to have different Reneg Times.

Refer to Editing Object Properties for information about editing properties common to all objects.


Queue Articles



Queue Object Frequently Asked Questions