UML case View

· Use Case View

The Use Case view is a model diagram of system functions observed by external users called participants. A use case is a functional unit in the system and can be described as an interaction between the participant and the system. The purpose of the use case model is to list the use cases and participants in the system, and to show which participant participates in the execution of which use case.

Figure 3-2 is an example of the ticket sales system. Participants include conductor, supervisor and public phone booth. A public phone booth is another system that accepts ticket booking requests from customers. In the application model of the ticket office, the customer is not a participant because the customer does not directly deal with the ticket office. Use Cases include purchasing tickets through a public phone booth or ticket conductor, purchasing booking tickets (only through the ticket conductor), and ticket sales supervision (as required by the supervisor ). Purchasing tickets and booking tickets include a common part-payment by credit card (a complete description of the ticket sales system also includes other use cases, such as ticket exchange and ticket acceptance ).

Use Cases can also have different levels. Use Cases can be described in other simpler use cases. In the interaction view, use cases are implemented as a collaboration in the interaction diagram.

Figure 3-2 use case diagram