Creating messages in sequence diagrams

In sequence diagrams, you can add synchronous and asynchronous messages to lifelines to represent communication between objects. You can also specify the signatures of messages.
To create a message:
  1. In the Palette, click a message type.
  2. In the 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.
Note: You can delay an asynchronous message by dragging the asynchronous message first horizontally and then vertically across existing messages to the target lifeline where you want to terminate the message.
Tip: You can also 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.
Related concepts
Sequence diagrams
Lifelines in UML diagrams

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