Goals for Presentation Explain the basics of software development methodologies Explain basic XP elements Show the structure of an XP project Give a few.

Goals for Presentation

• Explain the basics of software development methodologies

• Explain basic XP elements

• Show the structure of an XP project

• Give a few simple examples

Common Breakdowns

Problem: This isn’t what I wanted….

Problem: Six months of meetings and we have nothing to show for it…

Problem: When we went to install this, we found out this will need to be done in Perl. Is that a problem?

Problem: We just had this great idea. Forget what we told you last time. . .

Software Methodologies Formally Address…

• Requirement Analysis – Specifying what it needs to do

• System Design – Specifying how it will do it• Implementation Techniques - Specifying when it

will do it• Deployment strategies – Specifying where it will do

it

… Providing techniques to accomplish each.

Making this connection is requirement analysis. It is where most projects fail. It is the hardest job for most programmers. Methods for this are critical!

From XP Agile Universe

THE QuestionFor software developers

• Evolutionary – Assumes customers will change their minds.

• Light-weight – Minimizes excessive documentation• Fast – Produces tested software in 1 to 2 week

cycles• Rapid Assessment - Customers are activity involved

in all phases.

Hence, the term Agile

From the web site http://www.extremeprogramming.org/ It is an excellent resource and I strongly recommend reviewing it.

XP Element – User Story•They are a one to three sentence description of how the customer envisions using the system.•They are written by the customer.•They are written on 3” x 5” card.•The programmer assigns a time estimate to it in terms of ideal programmer weeks. •They are written in the language of the customer and not in programmer techno-jargon.

Note that no lengthy requirement document is produced.

XP Element – User Story

Some pages trigger the login mechanism and some don’t.

The list of pages that do/don’t is dynamic.

And the mechanism is triggered once per session.

One day

Taken from Extreme Programming in PracticeBy Newkirk and Martin

XP Element – Acceptance Test• The customer must supply an acceptance

test for each user story.• It is detailed scenario that will determine

whether the user story is operational.• The customer is responsible for verifying

accuracy.• All acceptance tests are run whenever the

system is changed in any way. Hence they should be automated.

XP Element – Acceptance TestAutomated testing is facilitated through unit test software.

Many packages to do this are on sourceforge.

A nice summary is found at

http://c2.com/cgi/wiki?TestingFramework

XP Element – Spike

• A small, simple program written to resolve uncertainty.

• Normally done to improve an time estimated associated with a user story.

• Expect to throw the effort away.

• Try not to spend much time doing it

User Story Summary

Customer Programmer

Writes Story

Specifies AcceptanceTest

Verifies AcceptanceTest

Provides Estimate Spike

XP Element - Velocity

• The velocity of a set of user stories is the sum of the estimates, which is given in terms of ideal programmer weeks.

• The velocity of an individual is the number of ideal days per real days. (For example, velocity = ½ means it takes two real days to do an ideal day.)

Project Structure

• Each Project is subdivided into a series of Releases. Typically a release is of 1 to 3 months.

• Each release is sub-divided into Iterations. Each iteration is 1 to 3 weeks.

• Velocity is held constant.

XP Element – Release & Iteration

Customer Programmer

Determines User StoryPriorities

Selects user storiesWithin the constraint

Determines Release Duration

Determinesvelocity

Limits number of user stories

XP Element – Release & Iteration

Iteration duration: 1 real weekRelease duration: 3 iterations or 3 real weeksIndividual velocity: 1/3 ideal days per real dayPair velocity: 2/3 ideal/real

15 real x 2/3 ideal/real = 10 ideal days allowed for the release roughly 3 ideal days for each iteration

Always work in pairs

No overtimeAllowed

!

XP Element - Task• The user stories selected for an iteration are broken

down into programming tasks.• These tasks are written on index cards like user

stories.• Tasks are written by programmers in the language of

programmers.• Programmers are allowed to select their own tasks.• A time estimate in ideal days is assigned to each task

by the programmer who selected it.

XP Element – Task Registration Servlet Task

Pull data from HTML input.If e-mail present in database go to “forgot password” screen.Else Generate password. Insert user into database. E-mail password to e-mail then go to login screen.

Jim 4 hours

Taken from Extreme Programming in PracticeBy Newkirk and Martin

XP Element –Iteration & Task

Customer Programmer

Determines User StoryFor iteration

Moves user stories toNext iteration, if needed

Determines Programming Tasks

Estimates time on task

Estimates iteration velocity

There are two time estimates for an iteration:

user story view & task view

Writing the Code

• Unit tests are written first.

• All programming is done in pairs. Two people work on a shared computer.

• Only one pair integrates at a time.

• No overtime!

Testing the code

• All code must have unit tests based on the acceptance tests.

• All code must pass unit tests before it can be released.

• Errors lead to new unit tests.

• Acceptance test scores are published.

From the web site http://www.extremeprogramming.org/ It is an excellent resource and I strongly recommend reviewing it.