29.4. Use Case Statechart Diagrams
A useful application of statechart diagrams is to describe the legal sequence of external system events that are recognized and handled by a system in the context of a use case. For example:
During the Process Sale use case in the NextGen POS application, it is not legal to perform the makeCreditPayment operation until the endSale event has happened.
During the Process Document use case in a word processor, it is not legal to perform the File-Save operation until the File-New or File-Open event has happened.
A statechart diagram that depicts the overall system events and their sequence within a use case is a kind of use case statechart diagram. The use case statechart diagram in Figure 29.2 shows a simplified ...
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