Introduction to eXtreme Programming (XP) Collaboration in Software Development Process.
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Transcript of Introduction to eXtreme Programming (XP) Collaboration in Software Development Process.
XP overview
A large percentage of software projects fail, due to a variety of problems we will see
Most of these problems are really issues of Design, Learning, and Collaboration in the software process
XP takes innovative approaches to improve Design, Learning, and Collaboration in the software process
Traditional Problems, XP solutions
Problem: Improper planning Not enough planning Too much planning: planning for situations that
will never occur Solution: XP says to quickly determine the
scope of the next (short) development cycle. Business priorities Technical feasibility Keep the plan updated as things change
Result: improved Design
Traditional Problems, XP solutions
Problem: Schedules blown at the last minute: Example: software project where all
development is done before integration Integration takes unexpectedly long
Solution: XP promotes Iterative development: Releases as small as possible
Solution: XP also includes constant integration
Result: managed risk
Traditional Problems, XP solutions
Problem: Design doesn’t fit together well because individual designers and implementers all have different ideas
Solution: In XP, a Metaphor, or simple shared story, is created for the entire project
Result: improved Collaboration
Traditional Problems, XP solutions
Problem: “Over-engineered” software Design for situations that will never occur Complexity causes defects
Solution: Extreme programming promotes maximum simplicity Implement the bare minimum that is needed now Add additional complexity as it is needed
Result: improved Design
Traditional Problems, XP solutions
Problem: The last few weeks in a 6 month long project is allocated for testing, but testing takes 4 more months instead
Solution: XP requires that programmers write unit tests for all code All tests must pass before development on new
items can continue Result: improved Design
Traditional Problems, XP solutions
Problem: Programmers know about bad sections of code, but do not fix them They don’t feel like they have time They are afraid to cause more trouble
Solution: XP makes Refactoring an official part of the development process. Programmers are empowered to fix problems
Result: improved Design
Traditional Problems, XP solutions
Problem: Programmers just code without thinking about the big picture, design problems and bugs result
Solution: XP requires that _all_ production code be written with 2 programmers behind the desk, one typing and one observing Pairs are “rotated” over time
Result: improved collaboration AND learning
Traditional Problems, XP solutions
Problem: One programmer won’t let others work on “his code,” thus nobody else understands it. Then he gets hit by a bus.
Solution: in XP, everyone owns all of the code. Everyone is allowed to work on any part of the system
Result: improved collaboration and learning
Traditional Problems, XP solutions
Problem: Programmer works 80 hours per week on a “death march” project trying to get a release out the door, wife leaves him, he quits to become a candle maker in Oregon
Solution: XP requires 40 hour weeks, and never allows overtime 2 weeks in a row
Result: Improved performance of programmers in many ways
Traditional Problems, XP solutions
Problem: Customer wants a High Heel shoe, development builds a Combat Boot Development solves the wrong problem
Solution: XP requires a “real life customer” on every team, ensuring that the project solves the right problems.
Result: improved collaboration (with customer)
Traditional Problems, XP solutions
Problem: Every programmer uses the language in different ways, formats their code and declares variables differently
Solution: XP implements coding standards so that a programmer new to a section of code can quickly attack the problem, not the style
Result: improved collaboration
Traditional Problems, XP solutions
Problem: A programmer spends hours on a problem that the person in the next cubicle could have answered in 2 minutes
Solution: XP includes daily meetings where each programmer shares what he or she is working on. This gets difficulties out in the open
Solution: Pair programming helps engineers keep track of what everyone on the team knows best
Result: improved collaboration
Senior Developer views of XP
Interviewed 2 Not a pure XP environment, but rapid
development These developers are familiar with XP Their names are Scott and Pete
Senior Developer views of XP
Planning Both agreed that a clear “forest” view is
necessary – understand the problem to solve Easier with short iterations
Short iterations Pete: major construction requires longer
iterations, at the risk of schedule predictability Suggests conservative scheduling for heavy
construction phases
Senior Developer views of XP
Metaphor Pete: One person sets the direction for a
product Consider feedback from others This is a “best practice” in other processes XP does not do this, more consensus based
Senior Developer views of XP
Simplicity Scott: strike a balance with Flexibility Pete: believes maximum simplicity can
still be flexible Testing
Pete: unit tests for every line difficult in practice Acceptance tests equally important
Senior Developer views of XP
Refactoring Both agree that refactoring has been
going on for a long time But making it an official part of the process
helps, especially for scheduling
Pair programming Pete hates pair programming
Feels that a solid engineer can beat any 2 engineers together
Senior Developer views of XP
Collective ownership Pete: Everyone should be familiar with all parts
of the system BUT there should be a “Design Owner” for important
sections, to maintain vision in the small
40 hour week Both feel this is possible in a stable world Pete would rather work more some of the time
40 hours is very arbitrary
Senior Developer views of XP
Customer on the team Pete: Real customers don’t know what
they want Give shallow feedback The “Vision Keeper” for the product should
know enough about the customers to be the “uber user”
XP – Strategies
Traditionalism is skeptical towards change
Paradigm shifts require strategies to tackle…
Planning Management Design Development Testing
XP - Planning Strategy
Goal: maximize value Game plan: low investment, high return Actors: developers, managers, clients Tools: user stories, CRC cards Actions: explore, commit, steer
XP - Management Strategy
Estimate: metrics, *relevance* Train: actors (programmers) Track: progress, compatibility Reorganize: teams, solutions, problem
space
XP - Design Strategy
Stick to the values! Simplicity Low initial investment Lightweight Incremental change
XP - Development Strategy
Quick iteration Small releases Collective ownership
Pair programming Refactoring Testing Continuous integration
XP - Testing Strategy
Unit Acceptance Parallel Stress Monkey !!}Test suite = Product specs.
You pass the tests, you fulfill the specs.
VCAPS – (Vehicle Cost and Profit System)
Ford Motor Company, 1993
Planning – Changing specs, priorities, regulations… caught up!!
Management – Separated from technical issues. Had a low view of developers’ efficiency.
Design – Mostly centralized, code got UGLY Leadership and Coaching – Low morale Integration: 20+ developers, race to the finish, ONE
integrator working nights Testing – Last two months. Bugs had a domino
effect.
VCAPS – XP to the rescue
Planning – CRC card culture: bigger picture Management – Integrated. Developers had
responsibility and authority. One-week iterations. Upper management worked as before.
PP – caught up more slowly, initial reluctance. Teaching techniques & level of experience. Pairs vs. Trios.
VCAPS – XP to … (cont’d)
Integration: small releases nip the problem in the bud.
Testing – smaller sized unit and functional tests: more targeted, easier to automate.
VCAPS - Conclusion
9 out of 12 XP practices embraced. Threw away old system and started afresh. Took one year for people to start enjoying. Management stopped seeing value.
Customers still wanted it. Got canned!! Lessons:
Transition slowly, one practice at a time. Management must take the lead. test vigorously, release frequently.
Introduction
Two programmers working side by side as stated by Kent Beck in Extreme Programming (XP) in 1996.
Objective is to improve software Quality and reduce Time-to-Market.
Pairs enjoy problem-solving process and outperform individual programmers.
They have greater confidence in their solutions.
Pair Jelling
Two programmers jointly produce one artifact.
One partner is the driver and has control of the pencil/mouse/keyboard and is writing the design or code.
The other person continuously and actively observes the work of the driver (watching for defects, thinking alternatives, looking up resources, and considering strategic implications of the work at hand).
Pair analysis and Pair design
It is important for the pair to collectively agree on the development direction and strategy outlined during these stages.
“Two brains are better than one” when performing analysis and design.
Significantly decreases the probability of proceeding with a bad design.
Other partner can think more strategically about implications of the design.
Avoid “design tunnel vision”.
Pair implementation
One programmer types into the computer while the other is actively engaged in observing, performing a continuous code review.
Efficient form of defect removal: removed right from the start.
Drawback: most programmers prefer to do a thorough review of their individual work and incorporate it into the project.
Pair Testing
Is the least critical part of the development cycle, as long as the pair develops the test cases together.
Testing discovers new bugs. Pair testing allows for different points of view on how to test an application, hence finding even more bugs.
Good Practices for Pair Programming
Don’t hit your partner: make sure your partner stays focused and on-task.
Put things back where they belong: have confidence but not too much confidence.
Clean up your mess: The “watch over the shoulder” technique epitomizes defect prevention and efficient defect removal.
Good Practices for Pair Programming
Don’t take things too seriously: “Ego-less programming”
Say you’re sorry when you hurt somebody while moving furniture: Appropriate workspace layout is critical to the pair success.
Wash your hands of skepticism before you start: develop an expectation of success and greet your collaborative partner.
Good Practices for Pair Programming
Flush: Pair programmers will work on something independently, when rejoining your partner review your work done separately.
When you go out into the world, watch out for traffic, hold hands and stick together: your work is done together, do not leave your partner apart.
Be aware of the power of two brains: You remember better, more knowledge and skills.
Good Practices for Pair Programming
Take a break from working together every afternoon: experiment new prototypes, deep-concentration, logical thinking is preferred to do it alone.
Live a balanced life – learn some and think some and draw and paint and sing and dance and work every day some.
Issues in Pair Programming
How do you create a good pair? One personality might consume the other. Or
two clashing personalities might not get work done.
Programmers tend to split work for more rote, routine and simple coding of a project.
Design review might be best in larger numbers (Design Review Boards). But Design alone is better in small numbers.
Issues in Pair Programming
What is a conducive workplace? Offices and cubicles are regular settings
for offices that hinder pair programming. “Like many kings, some managers use
divide-and-conquer tactics to rule their subjects, but programmers need contact with other programmers.” (Weinberg 1998).
Issues in Pair Programming
How much time should it occupy in a work day? Many programmers do not agree how
much time they should give for pair programming.
From all-day extreme, to few minutes a day.
Alternative Solutions: “Distributed pair programming” (Baheti, Gehringer, Stotts).
Interviews and Results
An experiment in Temple University showed that pair programmers produced 40% more quickly and effectively. Contrary to the notion of managers that believe that it would mean a 100% increase of production time.
96% stated that they enjoyed their job more than when they programmed alone.
Interviews and Results
Design is good in pairs, even better in 3-5 members. But more than that it hinders (never reach to an agreement).
Pair programmers is a positive form of peer pressure.
Simple tasks should be done alone, but by pair design you can identify which tasks need to be done in pairs.
Pairs enjoy their work more because they are more confident in their results.
Interviews and Results
Good way to bounce new ideas off. You can spend more time doing
challenging design and less time doing annoying debugging (due to better quality of product).
“We nailed that one” feeling. People who are forced to pair-program
despite their resistance might not do well.
XP: A Construction Management Perspective
Both software and construction industries are “project-driven.”
Software projects can be outsourced, while construction projects are heavy and fixed, built by local labor, having tremendous uncertainties.
Projects
What is a project?
Why project management?
Why so many projects fail?
How can we measure the “success” of a project?
Project Partnering
Background How construction industry
practices partnering? Initial partnering meeting Why it works? What software industry can
learn from it?
Virtual team design (VTD)
VDT
Simulation
Model
CONTROLS(“Assumed Model”)
INPUTS(variables)
MECHANISMS
(“Systems”)
OUTPUTS
(“Measures
of
progress”)