As discussed in Chapter 2, a swimlane is a visual region in an activity diagram that indicates the element that has responsibility for action states within the region. For example, the project management system may have the following swimlanes, which are illustrated in Figure 8-6:
Shows the action states that are the responsibility of a project manager. The swimlane makes it obvious that the project manager is responsible for entering data, thus the rather cumbersome action state name of Project Manager Enters Data may be shortened to Enter Data.
Shows the action states that are the responsibility of the project management system. Again, because the swimlane makes it obvious who (or what, in this case) is generating information, the rather cumbersome action state name of Project Management System Generates Information may be shortened to Generate Information.
Shows the action states that are the responsibility of a printer. Because of this swimlane, the rather cumbersome action state name of Printer Prints Information may be shortened to Print Information.
Notice how the use of swimlanes allows me to rename the action states to omit the responsible element for each action state.
In the UML, a swimlane is shown as a visual region separated from neighboring swimlanes by vertical solid lines on both sides and labeled at the top with the element responsible for action states within the swimlane. Figure 8-6 shows the swimlanes associated with the project management system.