In sequence diagrams, you can add a synchronous message
to a lifeline when you want the system to wait for the operation
to complete before it continues with a return message. You add an
asynchronous message when the sending participant does not wait
for the operation to complete before it continues with the next
step.
Note: When you create a synchronous
message, a return message is created by default. You can change
this default in the Preferences window.
To
add a synchronous or an asynchronous message:
- Open a sequence diagram that contains multiple
lifelines.
- In the Palette, click Synchronous Message or Asynchronous
Message.
- In the interaction frame, click the source lifeline and
then drag to the target lifeline.
- Complete one of the following steps:
- If the target lifeline represents a participant
of a structured classifier type, such as a class or component, in
the Enter Operation Name window, type a name
for the operation, and click OK.
- If the target lifeline represents a participant of a non-structured
classifier type, such as an actor, you can rename the selected message.
Note: If the source lifeline is the same as
the target lifeline, you create a self-directed message.