In communication diagrams, you can create messages to represent
the communication that occurs between participants in interactions. You can
add, delete, reposition, and assign new signatures to messages in an interaction
frame.
Before you can add messages, you must have a communication diagram
open that contains at least two lifelines that are connected by a message
pathway.
To create a message on a message pathway:
- In the Palette, click either Message or Reverse
Message.
- Click the message pathway to which you want to add the message.
As the following figure illustrates, the message is displayed as
an arrow on the message pathway, with an arrowhead that indicates the direction
of the message: forward or reverse. The forward portion of the message points
in the direction that you created the message pathway. The message label shows
the sequence number and the message name.

Note: By default, when you create a message on a message pathway,
both the synchronous call and the return message are added. To change this,
clear the Automatically create return message check
box in the Preferences dialog box.