Slide 10.1 CHAPTER 10 REQUIREMENTS PHASE

Slide 10.2 Overview l Requirements elicitation l Requirements analysis l Rapid prototyping l Human factors l Rapid prototyping as a specification technique l Reusing the rapid prototype l Management implications of the rapid prototyping model l Experiences with rapid prototyping

Slide 10.3 Overview (contd) l Techniques for requirements elicitation and requirements analysis l Testing during the requirements phase l CASE tools for the requirements phase l Metrics for the requirements phase l Object-oriented requirements? l Air Gourmet case study: Requirements phase l Air Gourmet case study: Rapid prototype l Challenges of the requirements phase

Slide 10.4 Requirements Phase l Misconception –Must determine what client wants l “I know you believe you understood what you think I said, but I am not sure you realize that what you heard is not what I meant!” [George Romney, US president candidate,1967] l Must determine client’s needs

Slide 10.5 Requirements Elicitation & Analysis Techniques l Interviewing (primary technique) l Structured versus unstructured interviews l Questionnaires l Forms analysis l Video cameras l Scenarios –Story boards –Trees l Rapid prototyping

Slide 10.6 Rapid Prototyping l Hastily built (“rapid”) l Key functionality l What the client sees l Experimentation and change l Languages for rapid prototyping –4GL (Smalltalk, Prolog, Lisp) –HTML, Perl, Visual C++, Java

Slide 10.7 Human Factors l Client and intended users must interact with the user interface l Human-computer interface (HCI) –Menu, not command line –“Point and click” –Windows, icons, pull-down menus l Human factors must be taken into account –Lengthy sequence of menus –Expertise level of interface –Uniformity of appearance (e.g., MS Office tools) –Use common sense

Slide 10.8 Rapid Prototyping as Specification Technique l No specification phase l Rapid prototype replaces specification document

Slide 10.9 Rapid Prototyping as Specification Technique l Specifications: Rapid prototype plus a list of additional features l Advantages –Speed –No ambiguities, omissions, contradictions l Disadvantages –Specification document is contract –Testing requires specifications –Maintenance requires specifications l Conclusion: Do not use rapid prototype as specifications

Slide Reusing the Rapid Prototype l Develop and refine rapid prototype till the final product l Build-and-fix l No specifications, no design l Quality l Maintenance l Real-time constraints

Slide Reusing the Rapid Prototype l Expensive option –Reuse rapid prototype l Cheap option –Discard rapid prototype l Use of different language for building prototype l Can safely retain (parts of) rapid prototype if –Computer generated (e.g., user interface) –Prearranged –Passes SQA inspections –This is not “classical” – not recommended!

Slide Other Uses of Rapid Prototyping l Management Implications –Immediate delivery –Instant maintenance –Waterfall model—get it right first time –Rapid prototyping—many changes, then discard –Increased interaction with clients

Slide Case for Rapid Prototyping l Not proven beyond all doubt l Experiment of Boehm, Gray, and Seewaldt (1984) –Seven different versions of product compared »four specified, three prototyped –Prototyping, specifying yielded equivalent performance –Prototyped versions had 40% less code, 45% less effort –Prototyped versions were lower on functionality and robustness, higher on ease of use and ease of learning –Specifying made integration easier

Slide Case for Rapid Prototyping (contd) l Important facts (not often mentioned) –Experiment on seven teams of graduate students –Three teams of size 2, and four teams of size 3 –Ten week duration –No maintenance l Treat results as indications, not facts

Slide Experiences with Rapid Prototyping l Analysis of 34 case studies [Gordon and Bieman, 1992] l 29 successes, 2 failures, 3 neutral –(But few failures are published!) l All agreed –User participation was essential, user needs were met l Not all issues were addressed in all case studies l (Only 16 mentioned ease of use, but all 16 were positive) l Choice of prototyping language was not important

Slide Controversy l Discard or retain rapid prototype? –Diametrically different processes used –18 recommended retention, 7 said discard –6 out of 6 large projects recommended retention

Slide Testing during the Requirements Phase l Aim: establish client’s real needs l Users must interact thoroughly with rapid prototype l Issues must reach client

Slide CASE Tools for the Requirements Phase l Language for Rapid Prototyping –Interpreted languages + environments (Lisp, Smalltalk) –HTML for user interfaces –4GL »Fewer statements »Often interpreted »Often powerful CASE tools l Danger of 4GL –Part of larger environment –Cheap solution: separate tool

Slide Metrics for the Requirements Phase l Quality, reliability? l Volatility, convergence l Changes during subsequent phases l Number of times each feature is used

Slide Object-Oriented Requirements Phase l On the one hand –The aim is to find the client’s needs –Objects don’t enter into it l On the other hand –Using an object-oriented language for the rapid prototype may help to identify classes

Slide Air Gourmet Case Study: Requirements Phase l Read pages 308 through 311 of the Fifth Edition of Object-Oriented and Classical Software Engineering

Slide Air Gourmet Case Study: Rapid Prototype l C and Java rapid prototypes are available on the Web at l For speed in implementation –Data are stored in fixed-size arrays –Only two reports are implemented (the other four are similar) –Interface is menu driven

Slide Portion of Rapid Prototype C Java

Slide Challenges of the Requirements Phase l Employees of the client organization feel threatened by computerization l Requirements team members must be able to negotiate l The client’s needs may have to be scaled down l Key employees of the client organization may not have the time for essential in-depth discussions l Flexibility and objectivity are essential l READ Chapter 10 of Schach