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.