You can specify the Message Type (or Sort) on page 4 of the Message tab in a Message’s definition. You can specify the following sorts:
•Asynchronous Signal: An asynchronous signal has an open arrow head.
•Asynchronous Call: An asynchronous call has an open arrow head.
•Create Message: An object creation Message has a dashed line with an open arrow head.
•Delete Message: An object deletion Message must end in a DestructionOccurrenceSpecification.
•Reply: A reply Message has a dashed line with an open arrow head.
•synchCall: A synchronous Message has a filled arrow head.
How to model an asynchronous (diagonal) message
To model a vertical message (as shown in the image below):
1 Draw the message between the Lifelines – it will draw orthogonally between the lifelines.
2 Select the line, and choose Format > Symbol Format > Line, and then change the line style to Straight – Any Orientation. You will then be able to move its handles to different places on the Lifeline, creating a diagonal line.
