Designing Your Model: Model-Code Correspondence : Activity Charts : Decomposition of Non-basic Activities : Communication and Synchronization Services between Activities : Signals

Signals

Signals indicate the occurrence of some event. However, since they are not queued, there is no information regarding how many such events occurred, until they are processed.

Also, these Task Event signals require that a specific task is addresses with a specific event, thus requiring knowledge of the application structure. The Task Event implementation is more efficient than ordinary or queued messages, however the task must be of type extended, which is not always possible or efficient.

The downside of requiring knowledge of the application is balanced by the improved performance. The weight assigned to these two issues will depend on the problem at hand.