Communication Diagrams
Figure25.23 shows a communication diagram that models the ATM executing a
Balance Inquiry. Objects are modeled in the UML as rectangles containing names in the
Form objects Name: Class Name. In this example, which involves only one object of each
type, we disregard the object name and list only a colon followed by the class name. [ Note:
Specifying the name of each object in a communication diagram is recommended when
Modeling multiple objects of the same type.] Communicating objects are connected with
solid lines, and messages are passed between objects along these lines in the direction
shown by arrows. The name of the message, which appears next to the arrow, is the name
of an operation (i.e., a member function) belonging to the receiving object—think of the
name as a service that the receiving object provides to sending objects (its “ clients”).