Sequence Diagrams Cont'd.

• Generic form shows several scenarios in the same diagram by using guards, branches and loops in the messages ([...], *); clutter??
• Instance form shows a particular scenario with no branches, guards or loops; too many??
• Returned messages may optionally be shown by dashed lines with solid arrow heads;
• Concurrently running objects are shown by activations, asynchronous messages and active objects in parallel;
• Labels are used for timing marks, iterations, descriptions of actions, constraints, etc.;
• Recursions are shown by message loop to the same object;
• Dynamic modelling of system behaviour using several sequence diagrams (a package): primary (main flow) & secondary (sub-flows and exceptions).