There are two ways to tell if the timing belt has been replaced. One is obvious-you are looking at a service receipt showing the replacement.
Swimlane diagrams are used whenever you need to show activities, tasks, or process steps which are being performed by different actors/roles. You can use swimlanes to group activities in an activity diagram or process flow by any category what you need: by role, by system, by department, etc.
Why use swim lanes. Swimlane visualizes actions performed by special resource types, organization elements or actions connected to a special location. Besides, Swim lanes make it possible to specify role of an executor and in this way to document responsibilities in a more accurate manner.