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Note

these are used to visualize concurrent activities happening in parallel, for example; audio playing alongside the game. that is a fork in the control flow of the system into parallel flows.

parallel flows can join into a single flow like audio ending with the end of the game.

one way to show concurrent activities is by making partitions, dividing them into different categories; for example:

• where it occurs.
• the user role involved.

an example is all video game activities concerning levels would be a partition and player activities in another partition, arrows crossing each lane show how activities interact across partitions.