Presentation on theme: "CS121: Software Development. Today Importance of software development Software methodologies Overview of course First assignment Administrative issues."— Presentation transcript:
Why study software development? Society has become increasingly dependent on software systems. –How many software systems do you interact with every day?
Why study software development? Society has become increasingly dependent on software systems. Failures in software systems can be costly and dangerous.
10 mi. Expedia Maps: I need to go to the airport (1999)
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: 5865.1 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) (4543.1 mi) 219:22 Arrive Baltimore-Washington International Airport, Maryland
Why study software development? Society has become increasingly dependent on software systems. Failures in software systems can be costly and dangerous
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)
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.
and then … 1983: First Therac 25 installed 1985-1987: 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.
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!
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 1991. 1987: Revised cost $4.3 billion, deployment slipped to 1995. 1994: FAA decided that the project would never be completed, and cancelled it. Net loss $1.5 billion
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
Is there hope? Software engineering: tools, techniques, and principles to promote software quality software engineering is an evolving field
Historical Perspective 1950s this is how to do it Code and fix
What is wrong with waterfall? Initial requirements are speculative
Requirements “The hardest single part of building a software system is deciding precisely what to build. ” Frederick P. Brooks Jr. in “No Silver Bullet”:
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”:
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.
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
Growth in requirements Source: Applied Software Measurement, Capers Jones, 1997. Based on 6,700 systems. % increase in requirements during project life
What is wrong waterfall? Initial requirements are speculative Initial designs are speculative
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.”
What is wrong waterfall? Initial requirements are speculative Initial designs are speculative Speculative decisions compound
Complexity vs. Productivity Source: Measures For Excellence, Putnam, 1992. Based on 1,600 systems. SLOC/Person Month
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
Historical Perspective Don’t bite off more than you can chew. 1990s 1970s 1950s
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.
Boehm Spiral Model Iterations:.5 – 2 years Risk analysis Prototype-based Boehm (1988) was first to clearly articulate the advantages of iterative development.
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
Scrum Model A small group is responsible for picking up the ball and moving it toward the goal.
Software projects come in all shapes and size some are easy, many hard
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
Objectives of CS121 Understand the problems Understand the various solutions to the problems Practice applying the solutions to a particular problem
Project You will work in teams to design and develop an educational computer game for social science teachers at Hillside Middle School, Kalamazoo, MI
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
Why educational games? Customer involvement Understanding an “other” user Useful product
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.
Phase 1 Competitive analysis High concept Management plan for phase 1 Customer elicitation Technology assessment Game Design Document (preliminary) Prototype Proposal
Assignments due next time Competitive analysis High Concept Initial management Plan (incl. trac set up) Details on the phase 1 project page Readings (Keller)
Reading for next time McConnel: requirements, software quality Wiegers: Requirement Traps Ambler: Big Requirements Up Front Trac Guide: wiki, ticket Keller: Goal breakdown
Daily quizzes Based on reading –McConnell –other articles linked to web page
Grading Project65% Midterm exam10% Final exam10% Daily quizzes 10% Class participation 5%
Today Complete intro questionnaires Make sure you have subscribed to the class mail list See me if you need accounts for: –Charlie –Knuth
Tomorrow I’ll email (and post) team assignments
Assignments Typically due on Monday Exceptions: –next week
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
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