Section 3.5. Time Events

3.5. Time Events

Sometimes time is a factor in your activity. You may want to model a wait period, such as waiting three days after shipping an order to send a bill. You may also need to model processes that kick off at a regular time interval, such as a system backup that happens every week.

Time events are drawn with an hourglass symbol. Figure 3-11 shows how to use a time event to model a wait period. The text next to the hourglassWait 3 Daysshows the amount of time to wait. The incoming edge to the time event means that the time event is activated once. In Figure 3-11, the bill is sent only oncenot every three days.

Figure 3-11. A time event with an incoming edge represents a timeout

A time event with no incoming flows is a recurring time event, meaning it's activated with the frequency in the text next to the hourglass. In Figure 3-12, the progress bar is updated every second.

Figure 3-12. A time event with no incoming flows models a repeating time event

Notice that there is no initial node in Figure 3-12; a time event is an alternate way to start an activity. Use this notation to model an activity that is launched periodically.