Designing sequence diagrams

Sequence diagrams describe message exchanges within your project. You can place messages in a sequence diagram as part of developing the software system. You can also run an animated sequence diagram to watch messages as they occur in an executing program.

Sequence diagram show scenarios of messages exchanges between roles played by objects. This functionality can be used in numerous ways, including analysis and design scenarios, execution traces, expected behavior in test cases, and so on.

Sequence diagrams help you understand the interactions and relationships between objects by displaying the messages that they send to each other over time. In addition, they are the key tool for viewing animated execution. When you run an animated program, its system dynamics are shown as interactions between objects and the relative timing of events.

Sequence diagrams are the most common type of interaction diagrams.

Note: IBM® Rational® Rhapsody® message diagrams are based on sequence diagrams. Message diagrams, available in the FunctionalC profile, show how the files functionality might interact through messaging (through synchronous function calls or asynchronous communication). Message diagrams can be used at different levels of abstraction. At higher levels of abstractions, message diagrams show the interactions between actors, use cases, and objects. At lower levels of abstraction and for implementation, message diagrams show the communication between classes and objects.

Message diagrams have an executable aspect and are a key animation tool. When you animate a model, the product dynamically builds message diagrams that record the object‑to‑object messaging.

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