Thresholds

Process blockages are modelled by Threshold objects that open and close according to various types of rules:

·         TimeSeriesThreshold.  Opens and closes when the value provided by a TimeSeries object meets various conditions.

·         ExpressionThreshold.  Opens and closes according to a specified expression that returns TRUE or FALSE (given by the values 1 and 0, respectively).

·         SignalThreshold.  Opens and closes when an entity is received by an EntitySignal object.

All types of Threshold objects share the following inputs and outputs.

Threshold Inputs

Keyword

Description

OpenColour

The colour of the threshold graphic when the threshold is open.

ClosedColour

The colour of the threshold graphic when the threshold is closed.

ShowWhenOpen

A Boolean value.  If TRUE, the threshold is displayed when it is open.

ShowWhenClosed

A Boolean value.  If TRUE, the threshold is displayed when it is closed.

Threshold Outputs

Output Name

Description

UserList

The objects that are stopped by this Threshold.

Open

If open, then return TRUE.  Otherwise, return FALSE.

OpenFraction

The fraction of total simulation time that the threshold is open.

ClosedFraction

The fraction of total simulation time that the threshold is closed.

OpenCount

The number of times the threshold's state has changed from closed to open.

ClosedCount

The number of times the threshold's state has changed from open to closed.

The response of an object to the closure of one of its Thresholds depends on which one of the following keywords was used.

Keywords that accept Thresholds

Keyword

Description

ImmediateThresholdList

A list of thresholds that must be satisfied for the object to operate.  Operation is stopped immediately when one of the thresholds closes.  If a threshold closes part way though processing an entity, the work is considered to be partly done and the remainder is completed once the threshold re-opens.

ImmediateReleaseThresholdList

A list of thresholds that must be satisfied for the object to operate.  Operation is stopped immediately when one of the thresholds closes.  If a threshold closes part way though processing an entity, the work is interrupted and the entity is released.

OperatingThresholdList

A list of thresholds that must be satisfied for the object to operate.  If a threshold closes part way though processing an entity, the remaining work is completed and the entity is released before the object is closed.

ReleaseThresholdList

A list of thresholds that must be satisfied for the object to operate.  If a threshold closes part way though processing an entity, the remaining work is completed, but the entity is retained until the threshold re-opens.

A given Threshold can appear in only one of these keywords at a time.  A single Threshold can be used by multiple objects.