1. UHD-CMS-Chp91 Requirements Phase Chapter 9

2. UHD-CMS-Chp92 Requirements Phase What must the new product be able to do? What the client needs?

3. UHD-CMS-Chp93 Requirements Functional Requirements: describe the interaction between the system and its environment –Environment: users, any other external system with which the system interacts Non-Functional Requirements: quantitative constrains e.g. –response time –accuracy

4. UHD-CMS-Chp94 Requirements Contd Pseudo-requirements: requirements imposed by the client that restrict the implementation of the system –implementation language –platform –process and documentation requirements: e.g. use of a specific formal specification language, etc.

5. UHD-CMS-Chp95 Requirement Elicitation Identify the actors: an actor is an external entity that interacts with the system Identify scenarios: a scenario is a concrete, focused informal description of a single feature of the system from the viewpoint of a single actor

6. UHD-CMS-Chp96 Questions to identify scenarios What are the tasks that the actor wants the system to perform What info does the actor access? –Who creates that data? –Can it be modified or removed? Which external changes does the actor need to inform the system about? How often? When? Which event does the actor need to be informed by the system about?

7. UHD-CMS-Chp97 Req. Analysis Techniques Interviews –Structured –Unstructured Send a questionnaire Examine the various forms Set up video cameras Scenarios Rapid Prototyping (most effective)

8. UHD-CMS-Chp98 Rapid Prototyping Exhibit the key functionality Reflects the functionality that the client sees Built quickly Built to be changed using 4GL and interpreted languages Using UNIX Shell or Lisp

9. UHD-CMS-Chp99 Human Factors Human-computer interface (HCI) User friendly –using windows, icons, menus,.. Menu-driven system is thoughtfully designed –multiple level of sophistication implies reduced learning times and lower error rates e.g., Macintosh

10. UHD-CMS-Chp910 Rapid Prototyping as a Spec. Tech. Fully or partially advantage –offers speed and accuracy Disadvantages –can not be used as a legal document –maintenance problems Should be used just for requirement analysis

11. UHD-CMS-Chp911 Reusing the Rapid Prototype Refine it, until it becomes the product In theory a fast development process In practice much like build-and-fix Reasons for throwing it away –cheaper in both short and long term –performance (specially in real time systems) to enforce not being reused –build it in a different language –use limited languages (e.g., hypertext) hybrid approach is used

12. UHD-CMS-Chp912 Other uses for Rapid Prototyping To resolve disagreements In many cases the only way to arrive to consensus quickly

13. UHD-CMS-Chp913 Management issues in regard to Rapid Prototyping Encourage clients for changing the product Changes be made quickly Not to wait for the real product It has not been proved beyond all doubts two aspects: –used solely for requirement analysis –in special cases could be used as a specification Rapid Prototyping has no good design requires interactions unlike waterfall model

14. UHD-CMS-Chp914 Experiences with Rapid Prototyping Gordon and Bieman report using published and unpublished case studies 33 out 39 where successful choice of languages is not critical partial retaining is important (larger porj.) fewer unnecessary features were implemented with it

15. UHD-CMS-Chp915 Joint Application Design (JAD) A techniques for requirement and specification phases The client takes an active role in the first two phases Productivity may increase 20 to 60 percent

16. UHD-CMS-Chp916 Comparison of Req. Analysis Techniques Interviewing (most important) –using forms –with relevant members of client organization Rapid Prototyping to meet client’s real needs –using JAD

17. UHD-CMS-Chp917 Case Tools for Req. Interpreted languages Case tools and language environments –smalltalk, interlisp, UNIX shell Hypertext two popular case tools –Demo II, Guide 4GL

18. UHD-CMS-Chp918 Metrics for the Req. Phase Measure of requirement volatility –can be used for scenario and interview techniques Number of requirements changes during the development process Number of time each feature is used –useful in Rapid Prototyping