Extreme programming: Difference between revisions

Revision as of 17:22, 3 December 2003

Revision as of 13:35, 10 December 2003

Line 1:

[[de:Extreme Programming]] [[es:Programación extrema]] [[fr:Extreme programming]] [[ja:エクストリーム・プログラミング]] [[nl:EXtreme Programming]] [[pl:Programowanie ekstremalne]]

'''Extreme Programming''' (XP) is a [[method]] in or approach to [[software engineering]], formulated by [[Kent Beck]], [[Ward Cunningham]], and [[Ron Jeffries]]. [[Kent Beck]] wrote the first book on the topic, "Extreme Programming Explained: Embrace Change" (ISBN 0201616416). It is the most popular of several [[agile processes]].

Fundamental characteristics of the method are:

*[[Incremental and iterative developments]] - small improvements[[improvement]]s after small ones

*continuous, often repeated automated [[unit test]], [[regression testing]]. See [[JUnit]].

*[[pair programming]]

*user interaction in the programming team ([[Onsite Customer]])

*[[refactoring]]

*shared code [[ownership]]

*[[simplicity]]

*[[feedback]]

These characteristics[[characteristic]]s are only derivatives[[derivative]]s of principles[[principle]]s that are known to be good, and are taken into extreme:

#[[Interaction]] between developers[[developer]]s and customers[[customer]]s is good. Therefore, an XP [[team]] is supposed to have a customer on site, who specifies and prioritises [[work]] for the team, and who can answer questions[[question]]s as soon as they arise.

#If learning is good, take it to extremes: Reduce the [[length]] of [[development]] and [[feedback cyclescycle]]s. Test early;

#Simple [[code]] is more likely to work. Therefore, extreme programmers only write code to meet actual needs[[need]]s at the [[present time]] in a [[project]], and go to some lengths to reduce [[complexity]] and [[duplication]] in their code.

#If simple code is good, re-write code when it becomes complex;

#[[Code reviewsreview]]s are good. Therefore XP programmers[[programmer]]s work in pairs[[pair]]s, sharing one [[screen]] and [[keyboard]] (which also improves [[communication]]) so that all code is reviewed as it is written;

#Testing code is good. Therefore, in XP, [[tests]] are written before the code is written. The code is considered complete when it passes the tests (but then it needs [[refactoring]] to remove [[complexity]]). The [[system]] is periodically, or immediately tested using all pre-existing automated tests to assure that it works. (See [[test-driven development]])

In general, Extreme Programming is believed to be useful for small teams[[team]]s under 12 persons[[person]]s. Some think it can be useful for larger teams while some consider the [[Rational Unified Process|RUP]] process is more appropriate in that case. However, XP has been demonstrated successfully on a team of over a hundred developers[[developer]]s. It's not that XP doesn't scale, just that few [[people]] have tried to scale it, and XPers refuse to speculate on this [[facet]] of the [[process]].

==Controversial Aspects==

* Detailed [[specification]]s are not written

* A [[customer representative]] is attached to the [[project]]

* Programmers[[Programmer]]s work in pairs[[pair]]s

* [[test-driven development]]

Most of the [[design activity]] takes place on the fly and incrementally,

starting with "the simplest thing that could possibly work" and adding

[[complexity]] only when it's required by failing tests. [[Unit-testing]] is a [[design discipline]].

''See also:'' [[Crystal Light Methods]] from [[Alistair Cockburn]]

==References & External Links==

* [[Kent Beck]], ''Extreme programming explained'', Addison Wesley, 2000

*[[Ward Cunningham]]'s website, http://www.c2.com/cgi/wiki?ExtremeProgramming - For more information on this and related topics

==External links==

* [[Ward Cunningham]]'s website, http://www.c2.com/cgi/wiki?ExtremeProgramming - For more information on this and related topics

* [http://www.nidelven-it.no/articles/extreme_programming Client oriented introduction to XP]

* [[Ron Jeffries]] web-mag http://www.xprogramming.com/

* [http://www.extremeprogramming.org/ extremeProgramming.org]

* [http://martinfowler.com/xp.html XP]

* [http://www.c2.com/cgi/wiki?ExtremeProgramming Wiki]

* [http://PairProgramming.com/ PairProgramming.com]

* [http://www.agilemanifesto.org/ agile Manifest]