3.2.1 Group actions

Actions may be grouped to represent a specific design concern. On the one hand the grouped entity is conceptual. Its boundary does not hinder data flow or control flow. Data flow must be directly connected to the input pins of the actions in the group, because a group action has no input pins. Control flow may also cross the group boundary and be directly connected to subactions. In this view, a group action is nothing but a logical view of its subactions.

On the other hand, when group actions are physically connected with control flows, they are placed in an execution sequence with their predecessors and successors. In this case, they follow the rule of sequential execution, i.e., they cannot be executed before all their predecessors are completed.