Creating messages in UML diagrams

In sequence diagrams, you can add create, destroy, synchronous and asynchronous messages to lifelines to represent communication between objects. You can also specify the signatures of messages.


  1. In the Palette, click a message type.
  2. In the diagram editor, in an interaction frame, click a source lifeline and drag the cursor to a target lifeline.
  3. Type a name for the message.


If you create a synchronous message, a return message is created automatically. If you start the message at the diagram frame with no source, a found message is created. If you create a message without a target, a lost message is created. A lost or found message is indicated by a dot at the source or target of the message.

What to do next

Note: To delay an asynchronous message, drag the asynchronous message first horizontally and then vertically across existing messages to the target lifeline where you want to terminate the message. You can also create an asynchronous message without a behavior execution specification.
Tip: To assign an operation to a message in an existing diagram, in the navigation view, click an operation and drag it onto a message in the interaction frame. The operation must belong to the target instance of the object or be visible to and in scope of the operation in an object.