Filter
Top Products
54 Model Driven Systems Development with Rational Products
Using activity diagrams
If the flow of events in a use case is complex, and especially if there are
numerous or complex alternative flows of events, it might be helpful to draw an
activity diagram to illustrate the entire flow of events. Activity diagrams have the
advantage of being able to show all alternate flows in one view, but have the
disadvantage of obscuring the main flow. Swimlanes can also be added to these
diagrams to show the responsibilities of the actors and the system.
We do not use activity diagrams in place of sequence diagrams in the MDSD
flowdown process. We have found that sequence diagrams have clearer
semantics for operations analysis, and that it is easier to extract traceability
information from the models using sequence diagrams.
5
For now, it should just
be clear that activity diagrams are used in MDSD as an optional view, to help
illustrate complex use case flows of events. We have seen many situations
where they were not used at all, with no ill affects, and others where they were
used only for complex use cases.
Understanding collaboration from a black-box
perspective
If we have completed our work through the previous MDSD step, what we have
now is a complete set of use cases. The next step is to answer the question,
What operations must the entity be capable of, in order to make possible all of
the usages described in these use cases? To answer this question, we perform
operation identification.
Examples of use case initiation:
This use case begins when the console operator selects to review the
program log.
This use case begins at 4:00 am daily.
This use case begins when the scheduling system requests the nightly
reconciliation process to begin.
This use case begins when it is time to check for the presence of rain.
5
Swimlanes and call operation actions in activity diagrams provide an alternative for those who are
more comfortable using activity diagrams. We do not treat this option in this document.