Agile Development Methods: Philosophy and Practice
CPSC 315 -Programming Studio
Spring 2009
History of Agile Methods
Particularly in 1990s, some developers reacted against traditional heavyweight software development processes.
New methods were being developed and tested,
e.g. extreme programming, SCRUM, Feature-driven development
Generally termed light processes
Representatives from several of these methods got together in Utah in 2001
Settled on term Agile as a way to describe these methods
Called themselves the Agile Alliance
Developed a manifesto and a statement of principles
Focuses on common themes in these alternative methodologies

12 Principles behind the Agile Manifesto
Our highest priority is to satisfy the customer through early and continuous delivery of valuable software.
Welcome changing requirements, even late in development. Agile processes harness change for the customer’s competitive advantage.
Deliver working software frequently, from a couple of weeks to a couple of months, with a preference to the shorter timescale.
12 Principles behind the Agile Manifesto
Business people and developers must work together daily throughout the project.
Build projects around motivated individuals. Give them the environment and support they need, and trust them to get the job done.
The most efficient and effective method of conveying information to and within a development team is face-to-face conversation.
12 Principles behind the Agile Manifesto
Working software is the primary measure of progress.
Agile processes promote sustainable development. The sponsors, developers, and users should be able to maintain a constant pace indefinitely.
Continuous attention to technical excellence and good design enhances agility.
12 Principles behind the Agile Manifesto
Simplicity–the art of maximizing the amount of work not done–is essential.
The best architectures, requirements, and designs emerge from self-organizing teams.
At regular intervals, the team reflects on how to become more effective, then tunes and adjusts its behavior accordingly.
Individuals and Interactions over Processes and Tools
People make biggest impact on success
Process and environment help, but will not create success
Strong individuals not enough without good team interaction.
Individuals may be stronger based on their ability to work on a team
Tools can help, but bigger and better tools can hinder more than help
Simpler tools can be better
Working Software over Comprehensive Documentation
Documentation important, but too much is worse than too little
Long time to produce, keep in sync with code
Keep documents short and salient
Focus effort on producing code, not descriptions of it
Code should document itself
Knowledge of code kept within the team
Produce no document unless its need is immediate and significant.
Customer Collaboration over Contract Negotiation
Not reasonable to specify what’ s needed and then have no more contact until final product delivered
Get regular customer feedback
Use contracts to specify customer interaction rather than requirements, schedule, and cost
Responding to Change over Following a Plan
Environment, requirements, and estimates of work required will change over course of large project.
Planning out a whole project doesn’ t hold up
Changes in shape, not just in time
Keep planning realistic
Know tasks for next couple of weeks
Rough idea of requirements to work on next few months
Vague sense of what needs to be done over year
Extreme Programming (XP)
One of the most well-known agile methods
Developed in 1990s
Kent Beck, 1996
Chrysler Comprehensive Compensation Project
Published book in 1999
Extreme Programming Practices
1. On-Site Customer
Customer is actively involved with development process
Customer gives User Stories
Short, informal stories describing features
Keep on story cards
2. Planning Game
Developers and customers together plan project
Developers give cost estimates to stories and a budget of how much they can accomplish
Can use abstract accounting mechanism
Later compare to actual cost, to improve estimates over time
Customer prioritizes stories to fit within budget
Extreme Programming Practices
3. Metaphor
Come up with metaphor that describes how the whole project will fit together
The picture in a jigsaw puzzle
Provides framework for discussing project in team
Tools and materials often provide good metaphors
4. Small Releases
Time between releases drastically reduced
A few weeks/months
Multiple iterations
Can have intermediate iterations between bigger releases
Extreme Programming Practices
5. Testing
Test-first programming
Unit testing frequently by developers
Acceptance tests defined by customers
6. Simple Design
Principles discussed in earlier lectures
Design should be quick, not elaborate
Pick the simplest thing that could possibly work
Resist adding stuff not ready yet
Extreme Programming Practices
7. Refactoring
Code gets worse with feature adds, bug fixes
Rewrite small sections of code regularly
Rerun all unit tests to know nothing broken
Means you should have designed comprehensive tests
8. Pair Programming
Discussed later
9. Collective Ownership
Anyone can edit anything
Errors are the fault of the whole team
Extreme Programming Practices
10. Continuous Integration
Commit changes frequently (several times a day)
Verify against entire test suite!
11. Coding Standards
Enables effective teamwork
12. Sustainable Pace
No overtime
Only exceptions in final week
Good estimation skills for budgeting will help ensure reasonable times
Time less likely to be wasted in pairs, bullpen rooms
Plan time each day for administrative work (<1 hour), breaks SCRUM Idea first appeared in a business journal in 1986 (applied to product development management). Used in software development and presented in 1995 paper. Term is based on rugby term Small cross-functional teams SCRUM Practices Product and release backlog A list of the features to be implemented in the project (subdivided to next release), ordered by priority Can adjust over time as needed, based on feedback A product manager is responsible for maintaining SCRUM Practices Burn-down chart Make best estimate of time to complete what is currently in the backlog Plot the time on a chart By studying chart, understand how team functions Ensure burndown to 0 at completion date By adjusting what' s in the backlog By adjusting the completion date SCRUM Practices The sprint The sprint is a ~1 month period after which some product is delivered Features are assigned from the product backlog to a sprint backlog Features divided into smaller tasks for sprint backlog Feature list is fixed for sprint Planning meeting Tasks can be assigned to team members Team members have individual estimates of time taken per item During sprint, work through features, and keep a burn-down chart for the sprint New functionality is produced by the end of the sprint After sprint, a review meeting is held to evaluate the sprint SCRUM Practices Scrum meeting 15 minute daily meeting All team members show up Quickly mention what they did since last Scrum, any obstacles encountered, and what they will do next Some team member volunteers or is appointed to be the Scrum Master - in charge of Scrum meeting, and responsible for seeing that issues raised get addressed Customers, management encouraged to observe SCRUM Practices Other Agile Methods Crystal Feature-driven development (FDD) Adaptive software development (ASD) Dynamic System Development Method (DSDM) Drawbacks and Challenges of Agile Methods Undefined goals Feature creep Neverending project with overruns Need clear, single, invested customer All-or-nothing adoption of techniques Some parts work only if lots of other aspects used Team size limited (smaller teams) Resources Used Agile methods: www.AgileAlliance.org
Agile methods (especially XP): Agile Software Development, by Robert C. Martin, Prentice-Hall 2003.
SCRUM: www.controlchaos.org
XP: eXtreme Programming in Action Practical Experiences from Real World Projects, by Martin Lippert, Stefan Roock, Henning Wolf, John Wiley and Sons, 2002.

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