Message (Sequence Diagram)

Sequence diagrams depict workflow or activity over time using Messages passed from element to element. These Messages correspond in the software model to Class operations and behavior. When you display a Sequence diagram, the Diagram Toolbox automatically switches to the Interaction Toolbox pages, containing the Message icon.

Access Click on the 'Message' icon, click on the source object and drag the cursor to the target object

(If the 'Message Properties' dialog does not display, right-click on the Message and on the 'Message Properties' menu option)

Create a Message on a Sequence diagram



See also


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.

You can also include operations that the element's classifier has inherited, in the list. To do this, select the 'Show Inherited Methods' checkbox.

Class Element Lifeline


If the available operations on the destination Class are not appropriate, click on this button and define a new operation in the destination 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.

Define Properties of Operations


Type any parameters that the Message has, as a comma-separated list.


(Optional) Type the actual value that corresponds to each parameter, as a comma-separated list.

Return Value

If the Message has a return value or type, specify it in this field.

Show Inherited Methods

Select this checkbox to include operations that the destination element's classifier has inherited, in the drop-down list of operations available in the 'Message' field.

Clear the checkbox to show only operations from the classifier itself.

Assign to

If the Message flow is from a Class element or Lifeline element with classifier that has defined attributes, click on the drop-down arrow 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 Class element 'Properties' dialog and add the required attribute.

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


(Optional) Type or select a stereotype for the connector (this is displayed on the diagram, if entered).


(Optional) Type an alias for the name of the Message.

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

Diagram Behavior Options


Type any conditions that must be true in order for the Message to be sent.


Type any constraints that might exist on when the Message is sent.

Is Iteration

Select the checkbox to indicate that the Message will iterate until the specified condition takes the value false. The condition statement on the diagram is prefixed by an asterisk (*).

Clear the checkbox to indicate that the Message will only be sent once within the process cycle, if the specified condition is true.

Start New Group

(For Communication diagram Messages). Select this checkbox to reset the Message (and all subsequent Messages) to a separate group with a new initial number.

Re-Order Messages


Click on the drop-down arrow and select 'Synchronous' or 'Asynchronous' as appropriate.

The value 'Synchronous' disables the 'Kind' field; synchronous Messages are always Calls.  

Call Asynchronous Signal Message


This field is enabled when the 'Synch' field is set to Asynchronous.

Click on the drop-down arrow and select either 'Call' or 'Signal', as appropriate.


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, set the field to '<none>'.

Is Return

If the Message you have created is a return message, select this checkbox.


(Optional) Type any explanatory notes, formatted if you prefer.


Click on this 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


Click on this button to close the dialog without saving any data you have entered.

Toolbox icon


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

Learn more