Event (UML)

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An event (Engl. Event ) is a model element in the Unified Modeling Language (UML), a modeling language for software and other systems.

The behavior of a system modeled with UML is always the behavior of cooperating instances of active classes . These instances are called active objects because they conceptually have an “active life of their own”. In contrast, passive objects show no behavior as long as there is no external impetus. If an active object wants to influence the behavior of other active or passive objects, a corresponding trigger is therefore necessary.

The UML 2 calls such a "trigger" event occurrence ( event occurrence , trigger ) and non- event . The UML2 defines an event as the type or type of occurrence of the event. This term is somewhat confusing, since it is neither in the German or even in English the normally assumed importance of event event corresponds. In both languages, event usually refers to the concrete occurrence, that is, something happens at a certain point in time.

Types of events

  • Time event ( TimeEvent ) stands for Self event that arrive at a given time. Time event can specify absolute or relative points in time.
  • Event call ( Call Event ) stands for Self event corresponding to the invocation of an operation on an object.
  • Signal event ( signal event ) represents event appearances, indicating the reception of a signal at the receiving object.
  • ChangeEvent ( ChangeEvent ) stands for event occurrences when the value of a Boolean expression changes from false to true in the course of changing variables.