1. 1 SYS366 More on (Systems) Use Cases

2. 2 Identifying Actors and Systems Use Cases Requirements Gathering Need to find out what the user requires in the system (user’s needs) Allows the Analyst to clearly understand the user’s requirements Need to describe the interaction between user of the system and the system itself Describes what the system is to do, not how it is going to do it

3. 3 Systems Use Case “Each use case delivers something of value to at least one of the actors. The concepts of actor goals and the delivery of value to the actors are fundamental to the successful discovery, definition, and application of use cases.”* *Use Case Modeling, Kurt Bittner & Ian Spence, Addison-Wesley, 2003, p.

4. 4 Systems Use Case “The use case starts when an actor does something, causing the system to do something in response. This dialog continues…until the system has done something useful during one interaction of the system for at least one actor.”* *Use Case Modeling, Kurt Bittner & Ian Spence, Addison-Wesley, 2003, p. 24

5. 5 Actors communicate with the system* To start the use case To ask for some data stored in the system, which the use case then presents to the actor To change data stored in the system by means of a dialog with the system To report that something special has happened in the system’s surroundings that the system should be aware of *Use Case Modeling, Kurt Bittner & Ian Spence, Addison-Wesley, 2003, p. 26

6. 6 Use cases communicate with the Actor* To report that something special has happened in the system that the actor should be aware of To ask an actor for help in making a decision needed to achieve a goal To delegate responsibility to an actor Use Case Modeling, Kurt Bittner & Ian Spence, Addison-Wesley, 2003, p. 26

7. 7 Systems Use Case One actor initiates a use case - However, after the use case has started, the use case can communicate with several actors.* *Use Case Modeling, Kurt Bittner & Ian Spence, Addison-Wesley, 2003, p. 26

8. 8 Sample Use Case Diagram System Boundary

9. 9 Use Cases How many use cases should a project have? As many as are needed to address the functionality of the system

10. 10 Introduction to Use Cases Carl’s OutDoors is a small business that rents various types of equipment for outdoor trips. Equipment such as camping equipment and canoes are rented. They also sell equipment for camping and canoeing and they organize outdoor adventure trips. Carl’s business has become very successful and he is having trouble keeping up with the growth. He needs to upgrade the system he currently has to handle the growing number of customers. Carl has asked you to help with the rental part of his business. Customers want to rent either camping equipment or canoes. When they are finished, the customers want to return the equipment. On occasion it is necessary for a customer to exchange the equipment they’ve rented. This could be for a variety of reasons. Such as, the equipment is defective (i.e. a tent might have a hole in it causing it to leak; or a canoe isn’t big enough for the canoeists and their equipment). As new equipment is received each season, Carl makes old equipment available for sale. Usually it is a final sale but customers are allowed to return equipment that is defective (i.e. a tent might have a hole in it causing it to leak; or a canoe that might have a hole in it as well causing it to let water seep in).