9.7. Events and MessagesParticipants change state on a timing diagram in response to events. These events might be the invocation of a message or they might be something else, such as a message returning after it has been invoked. The distinction between messages and events is not as important on a timing diagram as it is on sequence diagrams. The important thing to remember is that whatever the event is, it is shown on a timing diagram to trigger a change in the state of a participant. An event on a timing diagram is shown as an arrow from one participant's state-linethe event sourceto another participant's state-linethe event receiver (as shown in Figure 9-11). Figure 9-11. Events on a timing diagram can even have their own durations, as shown by event1 taking 1 unit of time from invocation by p1:Participant1 and reception by p2:Participant2Adding events to the timing diagram is actually quite a simple task, because you have the sequence diagram from Figure 9-3 to refer to. The sequence diagram already shows the messages that are passed between participants, so you can simply add those messages to the timing diagram, as shown in Figure 9-12. |