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Message (Sequence Diagram)


Sequence diagrams depict work flow or activity over time using Messages passed from element to element. These Messages correspond in the software model to Class operations and behavior.

Create a Message on a Sequence diagram



See also


Access the Sequence diagram.

The Interaction pages of the Toolbox display.




In the Interaction Relationships page, click on the Message icon, click on the source object and drag the cursor to the destination (target) object.

The Message Properties dialog displays (if not, right-click on the Message and select the Message Properties context menu option).




In the Message field, type the Message name:

If the Message flow is towards a Class element (dropped in from a Class diagram) or a Lifeline element having a classifier, and the destination Class has defined operations, you can click on the drop-down arrow and select an appropriate operation name; the Message then reflects the destination Class operations
If the available operations are not appropriate, you can click on the Operations button and define a new operation in the target element, using the Operations dialog
If you create a Message without making reference to the target Class operations, no new operation is added to the target Class


Class Element


General Properties of Operations


In the Parameters field, type any parameters that the Message has, as a comma-separated list.

If required, in the Parameter Values field type the actual value for each parameter, again as a comma-separated list.




If the Message is a return message, in the Return Value field enter the returned value or type.

It is possible to depict returns from a Self Message; simply create a second Self Message at the end of execution and select the Is Return checkbox in the Control Flow Type panel.




If the Message flow is from a Class element or Lifeline element with classifier that has defined attributes, click on the drop-down arrow in the Assign to field and select an appropriate attribute name.

The Message reflects the attributes from the source Class; you cannot add further attributes to the source Class here - if no appropriate attribute is listed, open the element Properties dialog and add the required attribute.

Otherwise, if required, type the name of the object to assign the message flow to.




In the Stereotype field, type or select an optional stereotype for the connector (this is displayed on the diagram, if entered).




If required, in the Alias field type an alias for the name of the Message.

On the diagram, the alias displays if the Use Alias if Available checkbox is selected on the Diagram tab of the Diagram Properties dialog.

The Alias displays instead of or as well as the Message name, depending on the setting selected in the Alias Usage panel of the Diagram Behavior page of the Options dialog.


Diagram Behavior Options


In the Condition field, type any conditions that must be true in order for the message to be sent.




In the Synch: field in the Control Flow Type panel, select Synchronous or Asynchronous as appropriate.


Asynchronous Signal Message


In the Lifecycle field, select New to create a new element at the end of the Message, or Delete to terminate the message flow at the end of the Message.

If neither case applies, leave the field at the default of <none>.




If required, in the Notes field type any explanatory notes.

You can format the notes using the Notes toolbar at the top of the field.




Click on the OK button to save the Message definition.

You can change the timing details of a message on the Timing Details dialog, and emphasize the sequence of closely-ordered messages using General Ordering
To toggle the numbering of messages on a Sequence diagram, select or deselect the Show Sequence Numbering checkbox on the Options dialog

Change the Timing Details

General Ordering

Sequence diagrams

Toolbox icon



You can also use the Message connector as an Information Flow, and realize information flows on the Message

Learn more