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Agile Process Models

Agile Process Models. P rescriptive models don’t work. It is unrealistic to not have changes. Why? The Agile Manifesto: Individuals and interactions over processes and tools Working software over comprehensive documentation Customer collaboration over contract negotiation

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Agile Process Models

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  1. Agile Process Models

  2. Prescriptive models don’t work • It is unrealistic to not have changes. Why? • The Agile Manifesto: • Individuals and interactions over processes and tools • Working software over comprehensive documentation • Customer collaboration over contract negotiation • Responding to change over following a plan

  3. The Agile approach • Fix time and resources, not features Functionality Time Resources FIXED Agile Prescriptive VARIABLE Time Resources Functionality

  4. The Agile approach • Effective and rapid response to change • Effective communication among all stakeholders • On-site customer • Rapid, incremental delivery of software

  5. The Agile process • Driven by customer descriptions of what is desired • These are translated into short-lived plans • Development is iterative • Adapts as changes occur • Little to no documentation • Why bother documenting what is likely to change? • Customer is on-site

  6. Popular Agile Processes • eXtreme Programming • Scrum

  7. eXtreme Programming • Very programmer-focused; take the good practices and do only those! • Simplicity • Communication • Feedback • Courage

  8. XP practices: Planning • Begins with customer-defined user stories • Agile team assigns each story a cost • Stories are grouped into deliverable increments • Commitment is made on delivery date • After the first increment this project velocity is used to define future increments

  9. XP practices: planning game Split a Story (Customer) Sort stories by value (Customer) “too big” Write a Story (Customer) Estimate a story (Developer) Declare velocity (Developer) “don’t know how” Spike a Story (Developer) Planning Exploration

  10. XP practices: user stories • Watered-down version of use cases • Written by customers, estimated by developers • Often on post-it notes • Replaces large documents

  11. XP practices: on-site customer

  12. More XP practices • Small releases • Continuous integration • Implies refactoring • System metaphor • Sustainable pace • 40 hours max/week

  13. XP practices: Pair programming • One developer writes, the other watches • Switch every two hours • Results in collective ownership • Need a coding standard

  14. XP practices: Test Driven Development • Write automated unit tests first (will all fail) • Only write code until all tests pass • Stop there; no extra features!

  15. When not to use XP • Customer requires documentation • Teams larger than 15 people • When you can’t get immediate feedback (embedded systems) • When it’s impossible to get people in the same room

  16. Scrum • Sprints, backlog, daily scrum meeting

  17. Criticisms of Agile approaches • Lack of scalability • Relies on mature team • May result in inefficient designs due to incrementality • Potentially expensive • On-site customer • Rework • Inefficiency

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