The Difference Between the Function and the Action Elements

The Reliability Module provides two elements: the Function element and the Action element.

Function elements are used to represent services that are carried out over a period of time such as an air-conditioning system, a battery, or a back-up generator. The Function element provides outputs that at any given time in a simulation inform other elements in the model whether or not it is functioning correctly. This allows for dependency relationships to be easily defined, for example a radio component might require a power-supply component to be operating.

Action elements are very similar to Function elements, but have several additional features to facilitate representation of activities or processes that are carried out discretely (as opposed to continuously) such as when a door latches closed, a switch opens or closes, an engine starts, or a message is delivered. The Action component waits for a triggering input to tell it to carry out its action. If its action succeeds, the element emits an ‘ActionOK’ event, and if it fails the element emits an ‘ActionFailed’ event.