Interaction diagrams

Instructor's Guide

introduction class diagrams use cases interaction packages state and activity discussion
Interaction diagrams are needed to clarify the actual behavior of a system, in particular the interaction between objects (or classes of objects) that result when executing a use case.

slide: Interaction diagrams

Interaction diagrams come in two forms, sequence diagrams and collaboration diagrams.

Sequence diagrams depict objects and their lifelines. When an object becomes active, the lifeline may be widened to a rectangle for the period of activity.

Collaboration diagrams depict the objects and their relations in a more static manner. Messages between objects, indicated by arrows, may be specified in greater or lesser detail. Also here, as a rule of thumb, details are given only when needed. To indicate message sequencing in collaboration diagrams numbering may be used, increasing or, as illustrated in slide uml-interact(b), branching.