Chapter 16. Interaction Overview Diagrams

Interaction overview diagrams are a grafting together of activity diagrams and sequence diagrams. You can think of interaction overview diagrams either as activity diagrams in which the activities are replaced by little sequence diagrams, or as a sequence diagram broken up with activity diagram notation used to show control flow. Either way, they make a bit of an odd mixture.

Figure 16.1 shows a simple example of one; the notation is familiar from what you've already seen in the activity diagram and sequence diagram chapters. In this diagram, we want to produce and format an order summary report. If the customer is external, we get the information from XML; if internal, we get it from a database. Small sequence diagrams show the two alternatives. Once we get the data, we format the report; in this case, we don't show the sequence diagram but simply reference it with a reference interaction frame.