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A wiki (IPA: IPA|[ˈwiː.kiː] <wee-kee> or Template:IPA <wick-ey> (according to Ward Cunningham) is a type of website that allows users to easily add and edit content and is especially suited for collaborative writing.

The term wiki also sometimes refers to the collaborative software itself (wiki engine) that facilitates the operation of such a website (see wiki software).

In essence, wiki is a simplification of the process of creating HTML pages combined with a system that records each individual change that occurs over time, so that at any time, a page can be reverted to any of its previous states. A wiki system may also provide various tools that allow the user community to easily monitor the constantly changing state of the wiki and discuss the issues that emerge in trying to achieve a consensus about the wiki content.

Some wikis allow almost completely unrestricted access so that people are able to contribute to the site without necessarily having to undergo a process of 'registration' as had usually been required by various other types of interactive websites such as Internet forums or chat sites.

The WikiWikiWeb is named after the "Wiki Wiki" line of Chance RT-52 buses in Honolulu International Airport. The name is based on the Hawaiian term wiki, meaning "quick", "fast", or "to hasten" (Hawaiian dictionary). Sometimes wikiwiki (or Wikiwiki) is used instead of wiki (Hawaiian dictionary).

Wiki is sometimes interpreted as the backronym for "What I know is", which describes the knowledge contribution, storage and exchange function.

Key characteristics

A wiki enables documents to be written collectively in a simple markup using a web browser. A single page in a wiki is referred to as a "wiki page", while the entire body of pages, which are usually highly interconnected via hyperlinks, is "the wiki"; in effect, a very simple, easier-to-use database.

A defining characteristic of wiki technology is the ease with which pages can be created and updated. Generally, there is no review before modifications are accepted. Most wikis are open to the general public without the need to register any user account. Sometimes session log-in is requested to acquire a "wiki-signature" cookie for autosigning edits. More private wiki servers require user authentication. However, many edits can be made in real-time, and appear almost instantaneously online. This can often lead to abuse of the system.

Pages and editing

In a traditional wiki, there are three representations for each page:

  • The user-editable "source code", which is also the format stored locally on the server. It usually is plain text, made visible to the user only when the edit operation shows it in a browser form.
  • A template (possibly internally generated) that defines layout and elements common to all pages.
  • The rendered HTML code produced by the server on the fly from the source text when a particular page is requested.

The source format, sometimes known as "wikitext", is augmented with a simplified markup language to indicate various structural and visual conventions. An often used example of one such convention is to start a line of text with an asterisk ("*") in order to mark it as an item in a bulleted list. Style and syntax can vary a great deal among implementations, some of which also allow HTML tags.

The reasoning behind this design is that HTML, with its many cryptic tags, is not especially human-readable. Making typical HTML source visible makes the actual text content very hard to read and edit for most users. It is therefore better to promote plain-text editing with a few simple conventions for structure and style.

It is also sometimes viewed as beneficial that users cannot directly use all the functionality that HTML allows, such as JavaScript and Cascading Style Sheets. Consistency in look and feel is also achieved, along with some extra safety for the user. In many wiki implementations, an active hyperlink is exactly as it is shown, unlike in HTML where the invisible hyperlink can have an arbitrary visible anchor text.

Wiki syntax (MediaWiki) HTML Rendered output
"''Doctor''? No other title? A ''scholar''? And he rates above the civil authority?"

"Why, certainly," replied Hardin, amiably. "We're all scholars more or less. After all, we're not so much a world as a scientific foundation&mdash;under the direct control of the Emperor."


&quot;<em>Doctor</em>? No other title? A <em>scholar</em>? And he rates above the civil authority?&quot;
&quot;Why, certainly,&quot; replied Hardin, amiably. &quot;We're all scholars more or less. After all, we're not so much a world as a scientific foundation&mdash;under the direct control of the Emperor.&quot;

"Doctor? No other title? A scholar? And he rates above the civil authority?"

"Why, certainly," replied Hardin, amiably. "We're all scholars more or less. After all, we're not so much a world as a scientific foundation—under the direct control of the Emperor."

(Quotation above from Foundation by Isaac Asimov)

Some recent wiki engines use a different method: they allow "WYSIWYG" editing, usually by means of JavaScript or an ActiveX control that translates graphically entered formatting instructions such as "bold" and "italics" into the corresponding HTML tags. In those implementations, saving an edit amounts to submitting a new HTML version of the page to the server, although the user is shielded from this technical detail as the markup is generated transparently. Users who do not have the necessary plugin can generally edit the page, usually by directly editing the raw HTML code.


While for years the de facto standard was the syntax of the original WikiWikiWeb, currently the formatting instructions vary considerably depending on the wiki engine. Simple wikis allow only basic text formatting, whereas more complex ones have support for tables, images, formulas, or even interactive elements such as polls and games. Many people switch between wiki engines. Because of the difficulty in using several syntaxes, many people are putting considerable effort into defining a wiki markup standard (see efforts by Meatball and TikiWiki).

Linking and creating pages

Wikis are a true hypertext medium, with non-linear navigational structures. Each page typically contains a large number of links to other pages. Hierarchical navigation pages often exist in larger wikis, often a consequence of the original page creation process, but they do not have to be used. Links are created using a specific syntax, the so-called "link pattern".

Originally, most wikis used CamelCase as a link pattern, produced by capitalizing words in a phrase and removing the spaces between them (the word "CamelCase" is itself an example of CamelCase). While CamelCase makes linking very easy, it also leads to links which are written in a form that deviates from the standard spelling. CamelCase-based wikis are instantly recognizable from the large number of links with names such as "TableOfContents" and "BeginnerQuestions". Note: It is easy for a wiki to render the visible anchor for such links "pretty" by reinserting spaces, and possibly also reverting to lower case.

CamelCase has many critics, and wiki developers looked for alternative solutions. The first to introduce so called "free links" using this _(free link format) was Cliki. Various wiki engines use single brackets, curly brackets, underscores, slashes or other characters as a link pattern.

Links across different wiki communities are possible using a special link pattern called InterWiki.

New pages in a wiki are usually created simply by creating the appropriate links on a topically related page. If the link does not exist, it is typically emphasized as a "broken link". Following that link opens an edit window, which then allows the user to enter the text for the new page. This mechanism ensures that so-called "orphan" pages (which have no links pointing to them) are rarely created, and a generally high level of connectedness is retained.


Most wikis offer at least a title search, and sometimes a full text search. The scalability of the search depends on whether the wiki engine uses a database or not; indexed database access is necessary for high speed searches on large wikis. On Wikipedia, the so-called "Go button" allows readers to directly view a page that matches the entered search criteria as closely as possible. The MetaWiki search engine was created to enable searches across multiple wikis.

Server-side versus client-side wiki

By far the most common wiki systems are server-side (Wikipedia is a server-side wiki). In essence, the edit, display and control functions are provided on the server through the wikiengine that renders the content into a HTML-based page for display in a web browser.

A client-side wiki system only requires the server to "serve" wiki files in much the same way as a web server allows HTML files to be retrieved using HTTP. In this type of wiki system, all the execution required to convert the underlying wiki text into an onscreen formatted display page resides in the client browser. Likewise, the editing tools and functionality reside with the browser.

The client-side wiki system parallels HTML in that the page becomes a rendering instruction for the browser to interpret. Client-side wiki systems may be little more than a code plugin to traditional web browsers.

Controlling changes

File:History comparison example.png
History comparison reports highlight the changes between two revisions of a page.

Wikis generally are designed with the philosophy of making it easy to correct mistakes, rather than making it difficult to make them. Thus while wikis are very open, they provide a means to verify the validity of recent additions to the body of pages. The most prominent, on almost every wiki, is the "Recent Changes" page—a specific list numbering recent edits, or a list of all the edits made within a given timeframe. Some wikis can filter the list to remove minor edits and edits made by automatic importing scripts ("bots").

From the change log, other functions are accessible in most wikis: the Revision History showing previous page versions; and the diff feature, highlighting the changes between two revisions. Using the Revision History, an editor can view and restore a previous version of the article. The diff feature can be used to decide whether or not this is necessary. A regular wiki user can view the diff of an edit listed on the "Recent Changes" page and, if it is an unacceptable edit, consult the history, restoring a previous revision; this process is more or less streamlined, depending on the wiki software used.

In case unacceptable edits are missed on the "Recent Changes" page, some wiki engines provide additional content control. It can be monitored to ensure that a page, or a set of pages, keeps its quality. A person willing to maintain pages will be warned of modifications to the pages, allowing him or her to quickly verify the validity of new editions.


The open philosophy of most wikis—of allowing anyone to edit content—does not ensure that editors are well intentioned. Wiki vandalism is a constant problem for wikis, though some sources with little relevant experience with wikis tend to exaggerate the danger of vandalism. Studies from IBM claim that most vandalism to Wikipedia is reverted in 5 minutes or less. For an alternative view, see the 2005-11-29 USA Today editorial by John Seigenthaler entitled "A false Wikipedia 'biography'".


Wiki software originated in the design pattern community as a way of writing and discussing pattern languages. The WikiWikiWeb was the first wiki, established by Ward Cunningham on March 25, 1995, as a complement to the Portland Pattern Repository. [1] He invented the wiki name and concept, and implemented the first wiki engine. Some people maintain that only the original wiki should be called Wiki (upper case) or the WikiWikiWeb.

Cunningham coined the term wiki after 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." [2] See also: List of computer term etymologies.

In the late 1990s, wikis increasingly were recognized as a promising way to develop private- and public-knowledge bases, and this potential 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 originally was based upon UseMod software, but later switched to its own, open source codebase, now adopted by many other wikis.

In the early 2000s, wikis were increasingly adopted in the enterprise as collaborative software. Common uses included project communication, intranets and documentation, initially for technical users. In December 2002, Socialtext launched the first commercial open source wiki solution. Open source wikis such as MediaWiki, Kwiki and TWiki grew to over 1 million downloads on the Sourceforge repository by 2004. Today some companies use wikis as their only collaborative software and as a replacement for static intranets. There is arguably greater use of wikis behind firewalls than on the public internet!

In 2005, the Los Angeles Times experimented with using a wiki in the editorial section of its web site. The Wikitorial project was soon shut down as vandals defaced it.

Wiki communities

The largest wikis are listed at List of largest wikis and Meatball: Biggest wikis. Today, the English-language Wikipedia is, by far, the world's largest wiki; the German-language Wikipedia is the second-largest, while the other Wikipedias fill many of the remaining slots. Other large wikis include the WikiWikiWeb, Wikitravel, World66 and, a Swedish-language knowledge base. The all-encompassing nature of Wikipedia is a significant factor in its growth, while many other wikis are highly specialized. Some also have attributed Wikipedia's rapid growth to its decision not to use CamelCase.

Many public wikis are listed at WorldWideWiki: SwitchWiki, which currently lists about 1000 public wiki communities (as of 2004-06-12).

One way of finding a wiki on a subject in which someone is interested is to follow the wiki-node network from wiki to wiki, or one could take a Wiki bus tour: TourBusStop. Wiki terminated domain names are growing in popularity to support specific niches.

For those interested in creating their own wiki, there are many publicly available "wiki farms", some of which can also make private, password-protected wikis. JotSpot, OddWiki, PeanutButterWiki, SeedWiki, Socialtext, WikiCities, and Wikispaces are seven such services; more at List of wiki farms. Wikipolls are also emerging. One site, Opinion Republic, is an experiment to capture public opinion and then converge on the most broadly accepted opinions.

Many wiki communities are private, particularly within enterprises as collaborative software. They are often used as internal documentation for in-house systems and applications.

For describing related wikis, there exist WikiNodes — pages on wikis describing related wikis. They are usually organized as neighbors and delegates. A neighbor wiki is simply a wiki that may discuss similar content or may otherwise be of interest. A delegate wiki is a wiki that agrees to have certain content delegated to that wiki.


See also


External links

Wiki Source: [3]