An action is a very atomic unit of business activity.  There is a primary distinction between mental actions and physical actions.  Both require energy, but are distinguished by the types of resources and devices involved.  Physical actions perform transformations, while mental actions provide the logic that directs processes through various functions.  It is sometimes useful to distinguish between actions described at a business level, and those that are performed by information systems.

Figure 9

Atomic actions are the activities that accomplish functions.  An action is performed by a (set of) role(s). It is triggered by a flow of material, energy, information, etc. and in turn initiates such flows.  Actions use resources and devices, and action is where we see a trade-off between individuals and devices.  Actions are at the level where it is most reasonable to analyze time durations that aggregate together to allow us to simulate business processes.