20 March

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20 March

• Extreme Programming

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Extreme Programming Project
http//www.extremeprogramming.org/
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User Stories

• Use cases
• Written by customer
• Used for planning
• Developers estimate by story
• Stories basis for iteration
• Used to build acceptance tests
• Remember that correctness equals meeting
  requirements

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System Metaphor

• Initial system design
• About the level that youre producing

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Spikes

• Technology explorations
• Focus on high risk items
• Typically considered throw-away code
• If not, needs to be agreed to by the whole team

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Release Planning

• Focused on iterations
• Can be defined by function or date
• Other is adjusted accordingly
• (Actually four parameters resources and quality
  are the other two that can be used to adjust)
• Planning adapts as the project progresses
• Project velocity is measured for each iteration
• Next iteration looks at planned vs. actual time
  and adjusts accordingly
• Each iteration has its own plan
• Developed at the beginning of the iteration

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Feedback Loops
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Iteration

• Scope of an iteration
• Should cover all parts of the system
• Only add the functions that you need for the
  current user story or stories
• Recommendation 3 weeks
• Moving people around
• Backup and training
• Code is owned by the whole team
• Pair programming
• Re-factoring

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Egoless Programming

• Weinberg 1971, The Psychology of Computer
  Programming
• During the cowboy era
• Observed that programmers needed to be team
  players
• Accept inspections and reviews
• Open to corrections and critiques
• Ten Commandments (Lamont Adams)
• But pride of ownership is critical to quality

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Pair Programming

• Two people working at a single computer
• Built-in backup and inspections
• Collaboration builds better code
• Mechanical model
• One drives, the other talks
• Keyboard slides between the two
• Logical model
• One tactical, the other strategic
• Both think about the full spectrum but bring
  different perspectives

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Pair Programming Experiments

• Typical numbers show the total manpower consumed
  not very different
• Numbers range, but no more than ¼ additional
  manpower
• Implication actual time is reduced
• Improved satisfaction also improves productivity
• Williams et al, Strengthening the Case for
  Pair-Programming

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Re-factoring

• Each iteration adds just the function needed
• If you continue to add new functions every two
  weeks, code can get messy
• Re-factoring is the cleaning up of the code at
  the end of the iteration
• Critical to maintaining quality code
• (Also applies to the design)

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Coding Rules

• The customer is always available.
• Code must be written to agreed standards.
• Code the unit test first.
• All production code is pair programmed.
• Only one pair integrates code at a time.
• Integrate often.
• Use collective code ownership.
• Leave optimization till last.
• No overtime.

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Communications

• Avoid unnecessary meeting
• Daily stand-up meetings
• In a circle
• No chairs
• Everyone must attend
• Minimizes other meetings
• Primarily informal as needed

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When to Use XP

• Types of projects
• High risk
• Poorly understood requirements
• Team
• Small size 2 to 12
• Needs to include customer
• Automated testing
• Timing issue

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What Makes a Project XP

• Paradigm - see change as the norm, not the
  exception, and optimize for change
• Values - honor the four values- communication,
  simplicity, feedback, and courage- in your
  actions
• Power sharing - business makes business decisions
  and development makes technical decisions
• Distributed responsibility and authority - people
  get to make the commitments for which they will
  be held accountable
• Optimizing process - you are aware of your
  software development process and when it is
  working and when it isn't, you are experimenting
  to fix the parts that aren't working, and you
  consciously acculturate new team members

Ward Cunningham, Ron Jeffries, Martin Fowler,
Kent Beck
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References

• Agile Methodologies www.martinfowler.com/articles/
  newMethodology.html
• Discussion http//xp.c2.com/ExtremeProgrammingRoad
  map.html