Extreme Programming

Extreme Programming (XP) is a method or approach to software engineering and the most popular of several agile software development methodologies. It was formulated by Kent Beck, Ward Cunningham, and Ron Jeffries. Kent Beck wrote the first book on the topic, Extreme programming explained: Embrace change, published in 1999. The second edition of the book, which appeared in 2005, delves more into the philosophy of Extreme Programming and describes it as being:

Controversial aspects

Extreme Programming also has its share of controversial aspects:

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• Detailed specifications are not created or preserved.
• Programmers are required to work in pairs - not all software developers expect to be asked to work this way.
• There is no Big Design Up Front. 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. This could result in more re-design effort than only re-designing when requirements change.
• A customer representative is attached to the project. This role can become a single-point-of-failure for the project and some people have found it to be a source of stress.

In 2003, Matt Stephens and Doug Rosenberg published a book under Apress called "Extreme Programming Refactored: The Case Against XP" which questioned the value of the XP process and suggested ways in which it could be improved (i.e. refactored). This triggered a lengthly debate in articles, internet newsgroups and web-site chat areas. The core argument of the book is that XP's practices are interdependent but that few practical organisations are willing/able to adopt all the practices; therefore the entire process fails. The book also makes other criticisms and it draws a likeness of XP's "collective ownership" model to socialism in a negative manner.

Related Topics:
Matt Stephens - Doug Rosenberg - Socialism

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Certain aspects of XP have changed since the book was published, in particular XP now accommodates modifications to the practices as long as the required objectives are still met. It also uses increasingly generic terms for processes. Some argue that these changes invalidate previous criticisms; others claim that this is simply watering the process down.

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Recently, authors have attempted to reconcile XP with the older methods that XP sought to replace (such as the waterfall method) in order to offer a unified method. See http://www.lux-seattle.com/resources/whitepapers/waterfall.htm for an example.

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