Used in a sequence diagram, a message is a communication between objects that conveys information and results in an action.
Messages extend from the lifeline of one object to the lifeline of another, except in the case of a message from an object to itself, in which case the message begins and ends on the same lifeline.
A message can be labeled with a name, an argument value, and a sequence expression. Variations of messages are represented in different ways:
Asynchronous message has a half-arrowhead.
Call has a solid, filled arrowhead.
Return has a dashed line.
Name a Message shape and add other property values
Open the element's UML Properties dialog box by double-clicking the icon that represents the element in the tree view or the shape that represents the element in a diagram.
Control which property values display on a shape in a diagram by right-clicking the shape, and then clicking Shape Display Options. In the UML Shape Display Options dialog box, select and clear options to display or hide property values.
Control which property values are displayed on the Message shape
Right-click the shape, click Shape Display Options, and then select or clear options to show or hide values.