A communication diagram shows the dynamic collaboration between elements. It is similar to the
sequence diagram and the intention is to focus on how the objects collaborate with each other.
Communication diagrams show the exchange of messages (or interactions) between objects as well
as the relationships (often called context).
Often a choice will be made to use either the sequence or the communication diagram. If showing
the time or sequence of events is most important, the sequence diagram should be used. If
showing context is most important the collaboration diagram should be used.
The communication diagram is drawn as an object diagram, where a number of objects are shown
along with the relationships between them. Message arrows are drawn between then to show the
flow of messages between the objects. Labels are placed on the messages that show the order
within which the messages are sent.
Example:
Example using stereotypes:
