Creating messages in communication diagrams

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 begin

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.


  1. In the Palette, click either Message or Reverse Message.
  2. Click the message pathway to which you want to add the message.
  3. From the popup window, create a new operation or select an existing operation to use as the message:
    • To create a new operation, click Create New Operation, type the name of the operation, select the classifier to own the operation, and click OK.
    • To use an existing operation, select it from the list in the popup or click Select Existing Operation to search the model for an operation.


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.

What to do next

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.