Learning UML 2.0

Chapter 9. Focusing on Interaction Timing: Timing Diagrams

Timing diagrams are, not surprisingly, all about timing. Whereas sequence diagrams (covered in Chapter 7) focus on message order and communication diagrams (see Chapter 8) show the links between participants, so far there has been no place on these interaction diagrams to model detailed timing information. You may have an interaction that must take no longer than 10 seconds to complete, or a message that should take no more than half the interaction’s total time to return. If this type of information is important to an interaction that you are modeling, then timing diagrams are probably for you.

Interaction timing is most commonly associated with real-time or embedded systems, but it certainly is not limited to these domains. In fact, the need to capture accurate timing information about an interaction can be important regardless of the type of system being modeled.

In a timing diagram, each event has timing information associated with it that accurately describes when the event is invoked, how long it takes for another participant to receive the event, and how long the receiving participant is expected to be in a particular state. Although sequence diagrams and communication diagrams are very similar, timing diagrams add completely new information that is not easily expressed on any other form of UML interaction diagram. Not having a timing diagram for an interaction is like saying, “I know what events need to occur, but ...