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CSE 308 Software Engineering

CSE 308 Software Engineering. Software Engineering Strategies. Software Project Outcomes. 2003 study of 280,000 SW Projects. Course Objectives. Acquire: Technical Knowledge Managerial Knowledge people, technology, processes. Acquire Technical Knowledge. Understand System Modeling

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CSE 308 Software Engineering

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  1. CSE 308Software Engineering Software Engineering Strategies

  2. Software Project Outcomes • 2003 study of 280,000 SW Projects

  3. Course Objectives • Acquire: • Technical Knowledge • Managerial Knowledge • people, technology, processes

  4. Acquire Technical Knowledge • Understand System Modeling • Learn UML • Practice different modeling methods: • Use Case Modeling • Object Modeling • Dynamic Modeling • Learn how to use tools • Component-Based Software Engineering

  5. Acquire Managerial Knowledge • Understand the Software Lifecycle • Process vs. Product • Different software lifecycles • Interface Engineering, Reengineering • Project Management

  6. The Best People Managers • Lead by example, not simply by making demands • Want their employees to succeed • Monitor and adjust • Make sure all team members are: • invested in the project • busy/utilized • making positive contributions • How? • People skills • Tech skills • Project management skills

  7. Software Engineering • Analysis: Understand the nature of the problem and break the problem into pieces • Synthesis: Put the pieces together into a large structure

  8. And for problem solving? • Techniques (methods) – formal procedures for producing results using some well-defined notation • Tools – instrument or automated systems to accomplish a technique • Methodologies – collection of techniques applied across software development and unified by a philosophical approach

  9. Software Engineering: Definition • A collection of techniques, tools, and methodologies that help with the production of: • a high quality software system • within a given budget, and • before a given deadline • … while change occurs What is your budget and deadline? How do you measure the quality of your project?

  10. Factors Affecting Quality of Software Complexity: • the system is so complex that no single programmer can understand it anymore Change: • the “Entropy” of a software system increases with each change: Each implemented change erodes the structure of the system • as time goes on, the cost to implement a change will be too high, and the system will then be unable to support its intended task.

  11. Why are Software Systems so Complex? • Difficult problem domain • Difficult dev. process • Software offers extreme flexibility • Capital investment constraints Usually leads to tight (impossible?) deadlines

  12. Dealing with Complexity 1. Abstraction 2. Decomposition 3. Hierarchy

  13. Abstraction • Inherent human limitation to deal with complexity • the 7 +- 2 phenomena • chunking: Group collection of objects • ignore unessential details: => Models

  14. Models Provide Abstractions • Many layers of models • Models for different stages: • System Models • Task Models • Issues Models

  15. System Models • Object Model • What is the structure of the system? • What are the objects and how are they related? • Functional model • What are the functions of the system? • How is data flowing through the system? • Dynamic model • How does the system react to events?

  16. Task Models • PERT Chart: • What dependencies are between tasks? • Gantt Chart • What order should tasks be scheduled? • Organizational Chart: • What is the organization of your team?

  17. PERT Charts

  18. Gantt Charts

  19. Organizational Charts

  20. Issues Model • What are the open and closed issues? • What constraints were posed by the client?

  21. Software Engineering Methodologies • Build-and-fix model • Waterfall model • Rapid prototyping model • Incremental model • Synchronize-and-stabilize model • Extreme programming • Spiral model Some texts use the term “prescriptive process models” Model to use is based on SW policies of your company

  22. Software Lifecycle Models • Life-cycle model (formerly, process model) • The steps through which the product progresses • Requirements phase • Specification phase • Design phase • Implementation phase • Integration phase • Maintenance phase • Retirement These phases usually overlap The problems are: 1. Mistakes can be made during the early phases and 2. The user can change his/her mind 3. “Feature creep”

  23. Build and Fix Model • Problems • No specifications • No design • Totally unsatisfactory • Need life-cycle model • Game plan • Phases • Milestones

  24. Waterfall Model • Rigid process • Documentation-driven Imagine buying a car by only reading the specs Feedback loops are rarely seen when this process is used

  25. Rapid Prototype Model • Make a simple prototype first • may be thrown away or completely replaced • prototype (i.e. research) vs. production teams • Useful for Game Dev. Projects • Game Dev Rule of Thumb: • have a game prototype 20% of way through process • Why? • fun is hard to quantify • prototype demonstrates core gamplay

  26. Incremental Model • Divide project into builds • system is built incrementally • testing after each build • Customer • review (and use) each build • evaluations may result in a change in requirements (for a subsequent build) • Builds add implementations of use cases Incremental model provides financial flexibility Ready to ship builds

  27. The Incremental Model

  28. Synchronize and Stabilize Model • Microsoft’s life-cycle model • Requirements analysis • interview potential customers • Draw up specifications • Divide project into multiple builds • Builds carried out by small teams working in parallel

  29. … Synchronize and Stabilize Model • At the end of the day: • synchronize (test and debug) • At the end of the build: • stabilize (freeze build) • Components always work together • Get early insights into operation of product

  30. Agile Programming Features • Early implementation • Successive builds • Collaboration with client • Importance of re-factoring Newer IDEs contain extensive refactoring features

  31. Extreme Programming • New approach • Stories (features client wants) • Estimate duration and cost of each story • Select stories for next build • Each build is divided into tasks • Test cases for task are drawn up first • Pair programming • Continuous integration of tasks

  32. Unusual Features of XP • Computers are put in center of large room • Client representative is always present • Cannot work overtime for 2 successive weeks • No specialization • Re-factoring Too soon to evaluate XP, but it appears questionable for large projects

  33. Spiral Model • Simplified form • waterfall model plus risk analysis • Precede each phase by • Alternatives • Risk analysis • Follow each phase by • Evaluation • Planning of next phase

  34. Simplified Spiral Model

  35. Conclusions • Different life-cycle models • each with own strengths • each with own weaknesses • Criteria for deciding on a model include • the organization • its management • skills of the employees • nature of the product (size, scope, complexity) • Best suggestion • “Mix-and-match” life-cycle model

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