Messages (Communication Diagrams)
A Message in a Communication diagram is equivalent in meaning to a Message in a Sequence diagram. It implies that one object uses the services of another object, or sends a message to that object. Communication Messages in Enterprise Architect are always associated with an Association connector between object instances. Always create the Association first, then add a Message to the connector.
Messages can be dragged into a suitable position by clicking and dragging on the message text.
Communication Messages are ordered to reflect the sequencing of the diagram. The numbering scheme should reflect the nesting of each event. A sequencing scheme could be:
2, 2.1, 2.2, 2.3
This would indicate the single sequence of events 2.1, 2.2 and 2.3 occurs within an operation initiated by event 2. This is the default pattern applied by Enterprise Architect.
Alternatively, the sequence could be:
2.1, 2.1.1, 188.8.131.52
2.2, 2.2.1, 184.108.40.206
This would indicate that two sequences of events can be initiated by event 2, and 2.1 and 2.2 are separate sequences, not consecutive events in one sequence. You can set the sequence pattern and order using the Properties window for the Message and the 'Sequence Communications' dialog.
If the target object is a Class or has its instance classifier set, the drop-down list of possible message names includes the exposed operations for the base type.