1. Functional Requirements – Use Cases Sriram Mohan/Steve Chenoweth (Chapters 14, 21 – Requirements Text) 1

2. What is a Functional Requirement? Functional requirements specify particular behaviors of a system. E.g., Suppose your “system” acts on “food” – “Cook food” is “functional.” Vs How well it cooks, or how fast, or how easily is not. Why? 2

3. What is a Use Case? A sequence of actions a system performs that yield an observable result of value to a particular actor Sequences of actions Performed by system of interest Observable result of value to a particular actor 3

4. Benefits – Requirements Management Easy to write and read Think from the perspective of an user Provides a clear idea of the “what” and the “how” User involvement Use cases tell a better requirement story Typically developers are encouraged and required to write use cases. Why ? 4

5. Benefits – Development Life Cycle Use cases become the vehicle for the following activities: ◦ Development of test plans for acceptance testing ◦ Creation of interaction design specifics, simply by adding detail to the use cases about “how” the actions will be done ◦ The basis for discovering a great OO design, based on the actors and their actions

6. Use Case Template A. Name B. Brief description C. Actors D. Basic flow E. Alternate flows F. Pre-conditions G. Post-conditions H. Other stakeholders I. System/sub-system J. Special requirements 6

7. Use Case Model - Development Steps 1. Identify the actors 2. Identify the use cases 3. Identify actor/use case relationships 4. Outline use cases 5. Refine use cases 7

8. 1. Identify the Actors Who uses the system? Who gets/provides information from/to system? Who supports the system? What other systems interact with this system? 8

9. 2. Identify the Use Cases What are the intentions of each actor with respect to the system? ◦ What are they going to use the system for? ◦ Does the actor provide some information? ◦ Does the actor need to be informed of something? 9

10. 2. Identify the Use Cases Give a descriptive name: ◦ Start with an action verb ◦ Describes goal or intent Give a one-sentence description 10

11. 3. Identify Actor/Use Case Relationships Draw a diagram showing relationships between actors and use cases 11 Eat food Buy food Parent Child

12. 4. Outline Use Cases Describe sequence of events in basic flow (sunny day scenario) Describe sequences of events in alternate flows (rainy day scenarios) 12

13. 5. Refine Use Cases Describe sequences of events for flows Describe pre-conditions Describe post-conditions Fill in special requirements 13

14. Pre and Post Conditions What is a pre-condition? What is a post-condition? 14

15. A. Name B. Brief description C. Actors D. Basic flow E. Alternate flows F. Pre-conditions G. Post-conditions H. Other stakeholders I. System/sub-system J. Special requirements Use Case Template 15

16. Microwave Example 16 User Cook Food

17. Cook Food Use Case – Slide 1 of 4 A. Name: Cook Food B. Brief description: User places food in microwave and cooks it for desired period of time at desired power level. C. Actors: User 17

18. Cook Food Use Case – Slide 2 of 4 D. Basic flow: 1.User opens door and places food in unit 2.User enters time for cooking 3.User tells microwave to start 4.Unit cooks food 5.Unit indicates it is done 18

19. Cook Food Use Case – Slide 3 of 4 E. Alternate flows 1.User cancels time before starting 2.User cancels cooking before finished 3.User selects reduced power level before pushing start button 4.Make sure you detail the alternate flows completely 19

20. Cook Food Use Case – Slide 4 of 4 F. Pre-conditions ◦ Unit is plugged in ◦ Unit is in ready state G. Post-conditions ◦ Food is cooked or user cancelled operation H. Special requirements ◦ Unit should indicate remaining time to finish while cooking ◦ Default power setting should be "high" 20

21. How do the use case and the storyboard fit? 21

22. How do you know you have collected enough use cases? 22

23. 23 Extending Use Cases Extend an existing use case instead of redefining it

24. 24 Microwave Extension User Cook Food Slice Food >

25. 25 Including Use Cases Frequent sequences of events may be defined as use cases Including a use case is like calling a subroutine

26. 26 Microwave Inclusion User Cook Food Set Timer >

27. 27 Cook Food Inclusion D. Basic flow: 1.User opens door and places food in unit 2.User performs Set Timer use case 3.User pushes start button 4.Unit cooks food 5.Unit beeps

28. RFC 2119 Will, Shall, Must Should May Is there a difference?

29. Extra Credit Can all functional requirements be specified using use cases? Explain Turn in your Answer using Angel (Lessons – Extra Credit – Week 3- Use Case Extra Credit) 29

30. Exam 1 Managing Software Requirements (Second Edition) ◦ Chapters 1 – 14(Except Chapter 11) ◦ Chapter 21 Interaction Design – Beyond Human Computer Interaction ◦ Chapter 7, 8 &11 30

31. In-Class Activity Develop use cases for the following features of the student feedback project 1. Instructors must be able to create and assign quizzes to their students 2. Instructors may analyze student responses to a quiz 3. Students must be able to provide anonymous feedback 31