A Wiki or wiki (pronounced "wicky", "weekee" or "veekee"; see pronunciation section below) is a website (or other hypertext document collection) that allows a user to add content, as on an Internet forum, but also allows that content to be edited by anyone.
Wiki (with a capital 'W') and WikiWikiWeb are sometimes used to refer specifically to the Portland Pattern Repository, the first-ever wiki. Proponents of this usage suggest using a lower-case 'w' for wikis in general. Wiki wiki comes from the Hawaiian term for "quick" or "super-fast."
Sometimes wikiwiki or WikiWiki or Wikiwiki are used instead of wiki.
Wikis generally follow a philosophy of making it easy to fix mistakes, rather than making it hard to make them. Thus, while wikis are very open, they also provide various means to verify the validity of recent additions to the body of pages. The most prominent one on almost every wiki is the so-called "Recent changes" page, which displays a list of either a specific number of recent edits or a list of all edits that have been made within a given timeframe. Some wikis allow the list to be filtered so that minor edits - or edits that have been made by automatic importing scripts ("bots") - can be excluded.
From the change log, two other functions are accessible in most wikis: the revision history, which shows previous versions of the page, and the diff feature, which can highlight the changes between two revisions. The revision history allows an editor to open and save a previous version of the page and thereby restore the original content. The diff feature can be used to decide whether this is necessary or not. A regular user of the wiki can view the diff of a change listed on the "Recent changes" page and, if it is an unacceptable edit, consult the history to restore a previous revision. This process is more or less streamlined, depending on the wiki software that is used.
In case unacceptable edits are missed on the "Recent changes" page, some wiki engines provide additional control over content. To make sure that a page or a set of pages keep their quality, it can be monitored. A person who is willing to maintain pages will then be warned of modifications of those pages, allowing him to verify the validity of new editions quickly.
The open philosophy of most wikis of letting anyone modify the content does not ensure that the editors are well-intentioned. Most public wikis shun mandatory registration procedures. Nevertheless, many of the major wiki engines (including MediaWiki, MoinMoin, UseModWiki and TWiki) provide ways to limit write access. Some wiki engines allow individual users to be banned from editing, which can be accomplished by blocking their particular IP address or, if available, their username. However, many Internet service providers (ISPs) assign a new IP address for each login, so IP bans can often be circumvented relatively easily and may prevent legitimate users from accessing features. To deal with this problem, temporary IP bans are sometimes used and extended to all IP addresses within a particular range, thereby ensuring that the vandal cannot edit pages within a given timeframe; the underlying assumption is that this is often sufficient as a deterrent. It may, however, still prevent some non-problem users from the same ISP from using the service for the duration of the ban.
A common defense against persistent "vandals" is to simply let them deface as many pages as they wish, knowing that they can easily be tracked and reverted after the vandal has left. This policy can quickly become impractical, however, in the face of systematic defacements born out of anger or frustration.
As an emergency measure, some wikis allow the database to be switched to read-only mode, while others enforce a policy in which only established users who have registered prior to some arbitrary cutoff date can continue editing. Generally speaking, however, any damage that is inflicted by a "vandal" can be reverted quickly and easily. More problematic are subtle errors inserted into pages which go undetected, for example changing of album release dates and discographies.
Many wikis allow pages to be protected from editing; in most wikis, this is used only in extreme and rare cases. Protected pages on Wikipedia, for example, can only be edited by administrators, who can also revoke the protection. Such actions are generally considered to go against the basic philosophy of wikis and therefore, they are usually avoided. At any given time, the English Wikipedia has perhaps thirty protected pages out of hundreds of thousands.
Given the relative simplicity of the wiki concept, many implementations now exist, ranging from very simple "hacks" implementing only core functionality to highly sophisticated content management systems. For detailed discussions, along with a list of some of the systems available, see Wiki software. They usually provide some kind of lightweight markup language.
Wiki software originated in the design pattern community as a way of writing and discussing pattern languages. The Portland Pattern Repository was the first wiki, established by Ward Cunningham in 1995  . Cunningham invented the wiki name and concept, and produced the first implementation of a wiki engine. Some people maintain that only the original wiki should be called Wiki (upper case) or the WikiWikiWeb. Ward's Wiki remains one of the most popular wiki sites.
Cunningham named the term wiki for the "wiki wiki" or "quick" shuttle buses at Honolulu Airport. Wiki wiki was the first Hawaiian term he learned on his first visit to the islands, when the airport counter agent directed him to take the wiki wiki bus between terminals. According to Cunningham, "I chose wiki-wiki as an alliterative substitute for quick and thereby avoided naming this stuff quick-web."  See also: List of computer term etymologies.
In the final years of the 20th century, wikis were increasingly recognized as a promising way to develop private and public knowledge bases, and it was this potential that inspired the founders of the Nupedia encyclopedia project, Jimbo Wales and Larry Sanger, to use wiki technology as a basis for an electronic encyclopedia: Wikipedia was launched in January 2001. It was originally based on the UseMod software, but later switched to its own open source codebase, which has now been adopted by many other wikis.
Today, the English Wikipedia is by far the world's largest wiki; the German language Wikipedia is the second largest, and the other Wikipedias fill many of the remaining slots. The fourth largest wiki, however, is Susning.nu, a Swedish language knowledge base running the UseMod software. The all-encompassing nature of Wikipedia has been a significant factor in its growth, while many other wikis are highly specialized. Some have also attributed Wikipedia's rapid growth to its decision not to use CamelCase. In any case, its position as the largest wiki has led to it sometimes being referred to as the Mother wiki on smaller, subject-specific wikis.
All known public wikis are listed at WorldWideWiki: SwitchWiki , which currently lists about 1000 public wiki communities (as of 2004-06-12).
The 30 largest wikis are listed at Meatball: Biggest wikis .
One way of finding a wiki on some subject you are interested in is to follow the Wiki Node Network from wiki to wiki. Or you could take a Wiki bus tour: TourBusStop.
See list of wiki.
- Aigrain, Philippe (2003). The Individual and the Collective in Open Information Communities. Invited talk at the 16th Bled Electronic Commerce Conference, Bled, Slovenija, June 11th 2003. Available at: http://www.debatpublic.net/Members/paigrain/texts/icoic.html
- Aronsson, Lars (2002). Operation of a Large Scale, General Purpose Wiki Website: Experience from susning.nu's first nine months in service. Paper presented at the 6th International ICCC/IFIP Conference on Electronic Publishing, November 6 - 8, 2002, Karlovy Vary, Czech Republic. Available at: http://aronsson.se/wikipaper.html
- Benkler, Yochai (2002). Coase's penguin, or, Linux and The Nature of the Firm. The Yale Law Jounal. v.112, n.3, pp.369-446.
- Cunningham, Ward and Leuf, Bo (2001): The Wiki Way. Quick Collaboration on the Web. Addison-Wesley, ISBN 0-201-71499-X.
- Jansson, Kurt (2002): "Wikipedia. Die Freie Enzyklopädie." Lecture at the 19th Chaos Communications Congress (19C3), December 27, Berlin. Online description: http://de.wikipedia.org/wiki/Benutzer:Kurt_Jansson/Vortrag_auf_dem_19C3
- Möller, Erik (2003). Loud and clear: How Internet media can work. Presentation at Open Cultures conference, June 5 - 6, Vienna.Available at: http://opencultures.t0.or.at/oc/participants/moeller
- Möller, Erik (2003). Tanz der Gehirne . Telepolis, May 9-30. Four parts: "Das Wiki-Prinzip", "Alle gegen Brockhaus", "Diderots Traumtagebuch", "Diesen Artikel bearbeiten".
- Nakisa, Ramin (2003). "Wiki Wiki Wah Wah". Linux User and Developer v.29, pp.42-48. Available at: http://184.108.40.206/lud29-Collaborative_Software-Wiki.pdf
- Remy, Melanie. (2002). Wikipedia: The Free Encyclopedia. Online Information Review. v.26, n.6, pp.434.
- "Tour bus stop" at MeatballWiki
- WikiWikiWeb (the first wiki)
- Wiki Community List
- Wiki Engines
- EvoWiki: How wikis evolve
- How did you come up with the idea for the Wiki? A video interview with Ward Cunningham
- Wiki Science : How to start a wiki (on Wikibooks) - help write the book on starting a wiki
- Possible wiki features
- Wikisearch: Blog about Wikis with multi-wiki search function