Control Operators

A Control Operator is a special type of Action Node which produces a Control Token on its output Parameter (i.e., activity parameter or action pin).  It is commonly used to dictate (i.e., control) the flow of Object Tokens in an Activity.  Similarly, it can be used to disable Object Token flow.  For example, if there is a streaming flow of Object Tokens entering an Activity, it may be useful to be able to “turn off the flow.”  This can be accomplished using a Control Operator Action which creates an output typed as ControlValue.  ControlValue is a SysML enumeration which holds the value of Enable or Disable.  In the example, there is a streaming flow of sensor data coming in to the Geolocate Sensor Data Activity Parameter.  It is continuously converted to Position Data and output to the Position Data Activity Parameter.  This Object Flow can be turned off if a Mode Selection is made, however.  A Mode Selection causes the «controlOperator» Action to either send, or not send, a Control Token to the sensor data conversion Action.  The «controlOperator» Action includes a Constraint which takes the modeSelection as an input and determines whether an Enable or Disable output is generated or not.  Convert to Position Data will not execute unless all of its inputs are present.

Example of Control Operator Usage

References:

Friendenthal, S., Moore, A., & Steiner, R. (2012) A Practical Guide to SysML. Waltham, MA: Morgan Kaufmann, pg 222-223, 580.