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CS121: Software Development. Today Importance of software development Software methodologies Overview of course First assignment Administrative issues.

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Presentation on theme: "CS121: Software Development. Today Importance of software development Software methodologies Overview of course First assignment Administrative issues."— Presentation transcript:

1 CS121: Software Development

2

3 Today Importance of software development Software methodologies Overview of course First assignment Administrative issues

4 “Software Development” …later in the millennium… Customer Developer Here it is … We need softwar e to …. Customer Developer

5 Key Processes Requirements Design Implementation Testing

6 “Software Development” …later in the millennium… Customer Developer Here it is … We need softwar e to …. Customer Developer Customer Developer It broke!

7 Key Processes Requirement Design Implementation Testing Maintenance

8 Key Processes Requirement Design Implementation (focus of CS70) Testing Maintenance

9 Why study software development? Society has become increasingly dependent on software systems. –How many software systems do you interact with every day?

10 Why study software development? Society has become increasingly dependent on software systems. Failures in software systems can be costly and dangerous.

11 10 mi. Expedia Maps: I need to go to the airport (1999)

12 Output reported in The Risks Digest Oct. 1, 1999 Excerpts from Expedia Maps directions: From: Laurel, Maryland To: Baltimore-Washington International Airport, Maryland Driving Distance: miles Time: 9 day(s) 3 hour(s) 22 minute(s) Time (hour:minute) Instruction 0:00 Depart Laurel, Maryland 1:01 Entering Delaware 1:17Entering New Jersey 3:24 Entering New York 3:51 Entering Connecticut 5:51 Entering Massachusetts 7:29 Entering New Hampshire 7:44 Entering Maine 12:20 Entering New Brunswick 20:20 Take the North Sydney-Argentia Ferry 34:32 Entering Newfoundland 36:35 Turn left onto Local road(s) ( mi) 219:22 Arrive Baltimore-Washington International Airport, Maryland

13 Why study software development? Society has become increasingly dependent on software systems. Failures in software systems can be costly and dangerous

14 Therac-25 Linear accelerators create high- energy beams that can destroy tumors with minimal impact on the surrounding healthy tissue Therac 25 was the first linear accelerator with dosage controlled solely by software (as opposed to hardware)

15 1983: Pre-release Safety Analysis Programming errors have been reduced by extensive testing on a hardware simulator and under field conditions on teletherapy units. Any residual software errors are not included in the analysis. Program software does not degrade due to wear, fatigue, or reproduction process. Computer execution errors are caused by faulty hardware components and by "soft" (random) errors induced by alpha particles and electromagnetic noise.

16 and then … 1983: First Therac 25 installed : Six massive-overdose accidents due to “software error” are reported. Overdoses caused severe burns and death. 1987: Recalled for extensive design changes, including hardware to safeguard against software errors in dosage.

17 Why study software development? Society has become increasingly dependent on software systems. Failures in software systems can be costly and dangerous Software design/development is HARD!

18 FAA 1981: FAA announced plans to modernize air- traffic control. 1985: IBM awarded contract. System estimate to have 1.5 million lines of code, cost $2.5 billion, and be deployed by : Revised cost $4.3 billion, deployment slipped to : FAA decided that the project would never be completed, and cancelled it. Net loss $1.5 billion

19 Stats on software projects 31.1% are canceled before they are finished 52.7% overrun their cost estimates by at least 189% 33.3% overrun their time estimates by 100%-200% 94% of all projects do a “restart” J. Johnson, “Creating Chaos,” American Programmer, July 1995

20 Is there hope? Software engineering: tools, techniques, and principles to promote software quality software engineering is an evolving field

21 Historical Perspective 1950s this is how to do it Code and fix

22 Historical Perspective 1950s

23 Historical Perspective 1970s that was soooooo wrong, but now we know, this is how to do it waterfall 1950s

24 Essential Processes of Software Development Requirements Design Implementation Testing

25 Software Life Cycle Model How to organize the key processes of software development

26 Waterfall Model Requirements Design Implementation Test with feedback

27 Historical Perspective 1970s 1950s

28 What is wrong with waterfall? Initial requirements are speculative

29 Requirements “The hardest single part of building a software system is deciding precisely what to build. ” Frederick P. Brooks Jr. in “No Silver Bullet”:

30 Requirements “No other part of of the work so cripples the resulting system if done wrong. No other part is more difficult to rectify later.” Frederick P. Brooks Jr. in “No Silver Bullet”:

31 1992 Iowa State study of safety-critical errors in software systems for Voyager and Galileo: The majority of safety-critical software errors were not caused in the design or implementation process. They were due to errors in the requirements specification. The systems as specified were flawed.

32 Requirements Customer’s don’t usually know what they want/need Even if they do know what they want/need, they are likely to change their minds

33 Growth in requirements Source: Applied Software Measurement, Capers Jones, Based on 6,700 systems. % increase in requirements during project life

34 What is wrong waterfall? Initial requirements are speculative Initial designs are speculative

35 Design Design Methods: Seeds of Human Futures (Jones, 1970) “The fundamental problem is that designers are obliged to use current information to predict a future state that will not come about unless their predictions are correct.”

36 What is wrong waterfall? Initial requirements are speculative Initial designs are speculative Speculative decisions compound

37 Complexity vs. Productivity Source: Measures For Excellence, Putnam, Based on 1,600 systems. SLOC/Person Month

38 What is wrong waterfall? Initial requirements are speculative Initial designs are speculative Speculative decisions compound As a result we build the wrong thing that doesn’t work any

39 Historical Perspective Don’t bite off more than you can chew. 1990s 1970s 1950s

40 Iterative Models In each iteration: Identify the objectives of the iteration Design a solution to achieve the objectives Implement the solution Test the implementation Each iteration is a mini-waterfall process.

41 Boehm Spiral Model Iterations:.5 – 2 years Risk analysis Prototype-based Boehm (1988) was first to clearly articulate the advantages of iterative development.

42 Agile principles Working software, delivered regularly, is the primary measure of progress High standards of excellence; test regularly and re-factor/redesign when necessary Customer involvement is critical Simplicity; just-in-time design/development Adaptability; embrace change Small, cross-functional, self-organizing teams of professionals

43 Scrum Model A small group is responsible for picking up the ball and moving it toward the goal.

44 RUP Life Cycle Management Environment Business Modeling Implementation Test Analysis & Design Preliminary Iteration(s) Iter. #1 Phases Processes Iterations within phases Supporting Workflows Iter. #2 Iter. #n Iter. #n+1 Iter. #n+2 Iter. #m Iter. #m+1 Deployment Configuration Mgmt Requirements ElaborationTransitionInceptionConstruction Iterations …

45 Extreme Programming

46 Do agile methods work? Standish CHAOS survey 16% 29% 53% 18% 31%

47 Software projects come in all shapes and size some are easy, many hard

48 Harder Large Open-ended, poorly understood Cutting edge technology Inexperienced personnel Stringent requirements Easier Small Well defined Ready-to-use tools, packages Experienced personnel Flexible requirements

49 Objectives of CS121 Understand the problems Understand the various solutions to the problems Practice applying the solutions to a particular problem

50 Project You will work in teams to design and develop an educational computer game for social science teachers at Hillside Middle School, Kalamazoo, MI

51 Why games? Games involve a range of problems that rarely show up in a single software project –User interface design –Computer graphics and sound –Simulation and modeling –Real-time –AI, networking, etc. You already have domain expertise Games are great projects for your portfolio Scope of the game project can be “easy” to adjust

52 Why educational games? Customer involvement Understanding an “other” user Useful product

53 Overview of Project Phase 1: Develop game concept Phase 2: Design game/software Phase 3: Evaluate, refine, add content But not waterfall. Each phase will have involve several iterations/deliverables.

54 Phase 1 Competitive analysis High concept Management plan for phase 1 Customer elicitation Technology assessment Game Design Document (preliminary) Prototype Proposal

55 Assignments due next time Competitive analysis High Concept Initial management Plan (incl. trac set up) Details on the phase 1 project page Readings (Keller)

56 Reading for next time McConnel: requirements, software quality Wiegers: Requirement Traps Ambler: Big Requirements Up Front Trac Guide: wiki, ticket Keller: Goal breakdown

57 Daily quizzes Based on reading –McConnell –other articles linked to web page

58 Grading Project65% Midterm exam10% Final exam10% Daily quizzes 10% Class participation 5%

59 Today Complete intro questionnaires Make sure you have subscribed to the class mail list See me if you need accounts for: –Charlie –Knuth

60 Tomorrow I’ll (and post) team assignments

61 Assignments Typically due on Monday Exceptions: –next week

62 Next week Wed – you will meet with the customer 1 team will do an “elicitation” in class (the guinea pigs are guaranteed the full 10 point credit for the actual elicitation – volunteers?) the rest will do it after class Wed. or Thurs. morning – post all available times on your wiki

63 Sample questions from today What are the key processes to software development? What is a software life cycle model? What is the waterfall model? What are its problems? How do iterative and agile models differ from the waterfall model? How do iterative and agile models differ from each other? What is the Boehm Spiral model and why is it important? Name two different agile process methods


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