1. Sept. 11, 2003CS 509 - WPI1 CS 509 Design of Software Systems Lecture #2 Thursday, Sept. 11, 2003

2. Sept. 11, 2003CS 509 - WPI2 §Add/Drop, group changes if needed §Questions §Quiz #1 §Requirements Discussion §Review Chapter 4 §Requirements Exercises §Discussion about Meeting Coordinator Class Format for Today

3. Sept. 11, 2003CS 509 - WPI3 Questions? §From last week’s class §From the reading §Anything else? l Hold off on MC Requirements questions for now. §Comment about development schedule – Implementation phase

4. Sept. 11, 2003CS 509 - WPI4 Quiz #1 Choose 5 questions to answer. You have 15 minutes.

5. Sept. 11, 2003CS 509 - WPI5 Requirements Discussion §Define Requirements: l What are they? l What goes into a requirements document? §Why do we need requirements? What purpose do they serve? §What can go wrong without them? §Why do we write Requirements documents?

6. Sept. 11, 2003CS 509 - WPI6 Requirements Elicitation Chapter 4

7. Sept. 11, 2003CS 509 - WPI7 Requirements Activities §Identify Actors §Identify Participating Objects §Identify Scenarios §Identify Use Cases §Identify relationships among use cases §Identify nonfunctional requirements

8. Sept. 11, 2003CS 509 - WPI8 Participating Objects §Actors l Who will use the system? l What parts of the system are used by which actor? §Other participating objects l Main concepts in application domain l Glossary of terminology: define terms same concept always has same name different concepts always get different names

9. Sept. 11, 2003CS 509 - WPI9 Scenarios & Use Cases §Scenarios are concrete, focused descriptions of a single feature of the system §A scenario is an instance of a Use Case §Use Cases are generalizations of scenarios §A Use Case captures all possible scenarios for a given piece of functionality

10. Sept. 11, 2003CS 509 - WPI10 Heuristics §What are Heuristics? §How do they differ from an Algorithm? §See box on top of page 113.

11. Sept. 11, 2003CS 509 - WPI11 Use Case Relationships §Communication relationships - indicate flow of information §Extend relationships - used for exceptional, optional or seldom-occurring cases §Include relationships - used for sub-cases which are shared by two or more use cases §Do you need these relationships in your Requirements document?

12. Sept. 11, 2003CS 509 - WPI12 Nonfunctional Requirements §User-visible aspects of the system §Not directly related to functional behavior §Have impact on design, development and cost of the system §See bullet list on page 119 in textbook

13. Sept. 11, 2003CS 509 - WPI13 Objectives & Success Criteria §What are typical objectives of a SW system? l Fast execution – how fast is fast enough? l Small in storage requirements – how small? l User friendly l Other examples? §What are success criteria? l How do you determine whether you’ve met an objective?

14. Sept. 11, 2003CS 509 - WPI14 Other notes about RAD §See outline on page 126. §2 sections for terminology: 1.4, 4. l Use what seems applicable §Sample Requirements Doc on course web site l Functional requirements could be expanded l Scenarios section incomplete – needs more work l Use Cases only just started

15. Sept. 11, 2003CS 509 - WPI15 Requirements Exercises

16. Sept. 11, 2003CS 509 - WPI16 Exercise #1 - Definitions (From textbook, exercise #9, page 128) §Get out a clean sheet of paper §Write down a brief definition for the term “menu” §Pass your papers up to the front §Compare definitions l Are there differences? If so, what are they? l Discuss.

17. Sept. 11, 2003CS 509 - WPI17 Exercise #2 - Communication Design and build a “chair” §Definition - what is a chair? l What is its purpose? l What are its salient characteristics? §Design decisions: l What choices are there? l Who decides?

18. Sept. 11, 2003CS 509 - WPI18 Meeting Coordinator Requirements Elicitation

19. Sept. 11, 2003CS 509 - WPI19 For Next Time Analysis – Chapter 5