This example shows an activity diagram for the theatre ofﬁce. This diagram shows the activities involved in planning a show.
1. Arrows show sequential dependencies—for example, shows must be picked before they are scheduled.
2. Heavy bars show forks or joins of control. For example, after the show is scheduled, the theatre can begin to publicize it, buy scripts, hire artists, build sets, design lighting, and make costumes, all concurrently. Before rehearsal can begin, however, the scripts must be ordered and the artist must be hired.
An activity diagram is helpful in understanding the high-level execution behavior of a system, without getting involved in the internal details of message passing required by a collaboration diagram.