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.
A swimlane diagram (also sometime called a cross-functional diagram) documents the steps or activities of a process flow or workflow. More specifically, a swimlane diagram groups these activities into swimlanes which are horizontal or vertical columns that contain all of the activities which fit into the category represented by that swimlane.