Activity cycle diagram

An activity cycle diagram (ACD) is a graphical modeling tool to depict interactions among objects in a system.

Origin
The ACD is a modeling tool that was developed in 1960 following the flow diagram method of K.D. Tocher. It pertains to the activity-based paradigm of system modeling, as opposed to process-oriented or event-based paradigms. The activity-based modeling is a natural way to represent the knowledge about a system in the activity paradigm of discrete event simulation.

Characteristics
The activity cycle diagram is characterized by its focus on the life cycle of the components of a system, distinguishing for each component a "dead" state and an "active" state.

Implementation
In activity-based modeling, the dynamics of system is represented as an ACD which is a network model of the logical and temporal relationships among the activities. An ACD is easily implemented with the activity scanning method of simulation execution.