1 March

Extreme programming

Presentations

Tuesday Campus Tour Sami Says Hawks

Thursday Read2Me UNCSET Oral Lab NetVis

If helpful, invite your client

Software Engineering Elaborated Steps Concept Requirements Architecture Design Implementation

Extreme Programming Unit test Integration System test Maintenance

What it is

Complete development process First code drop is 2-3 weeks after start Customer a part of the development

team Iterative development to the max Derive requirements with customer

through hands-on experimentation Agile methodology

XP Bills of Rights Developer has a right to

Clear requirements and priorities Determine how long a requirement will take to implement Revise estimates Always produce quality code

Customer has a right to An overall plan See progress in a running system Change requirements and priorities Be informed of changes to schedule and have input as to

how to adapt Cancel in the middle and still have something to show for

the investment

XP Bills of Rights Developer has a right to

Clear requirements and priorities Determine how long a requirement will take to implement Revise estimates Always produce quality code

Customer has a right to An overall plan See progress in a running system Change requirements and priorities Be informed of changes to schedule and have input as to

how to adapt Cancel in the middle and still have something to show for

the investment

XP Value System

Communication Focus on people, not documentation

Simplicity Of process and code

Feedback Mechanism to make useful progress

Courage To trust in people

People Most important factor in the quality of

software is the quality of the programmers If your life depended on a particular piece

of software, what would you want to know about it?

Bollinger (2001): that the person who wrote it was “both highly intelligent and possessed by an extremely rigorous, almost fanatical desire to make their program work the way it should.”

Knowledge Workers … prefer closed offices but communicate better

in open ones congregate in particular geographical areas move around in the course of their work collaborate concentrate work in the office communicate with people who are close by don't care about facilities gewgaws

Davenport, Why Office Design Matters 2005

Fundamental Conflict

Solutions?

Extreme Programming Project

http://www.extremeprogramming.org/

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

System Metaphor

Initial system design About the level that you’re

producing

Spikes

Technology explorations Focus on high risk items Typically considered throw-away

code If not, needs to be agreed to by

the whole team

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

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

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

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

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”

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)

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.

Communications

Avoid unnecessary meeting Daily stand-up meetings

In a circle No chairs Everyone must attend

Minimizes other meetings Primarily informal as needed

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

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

References

Agile Methodologies www.martinfowler.com/articles/newMethodology.html

Discussion http://xp.c2.com/ExtremeProgrammingRoadmap.html