These wiki websites are often also referred to as wikis; for example, Wikipedia is one of the best known wikis.^[1] Wikis are being installed by businesses to provide affordable and effective Intranets and for Knowledge Management. Ward Cunningham, developer of the first wiki, WikiWikiWeb, originally described it as "the simplest online database that could possibly work".^[2]

Wiki Wiki (/wiːkiː wiːkiː/) is a reduplication of wiki, a Hawaiian word for "fast". In English, "wiki" is an abbreviation of it.

History of wikis

There were several historical antecedents to the wikis, which is the name used to refer to a website with pages that can be edited by any visitor. One of the earliest precursors was Vannevar Bush's vision of a microfilm hypertext system which he called the "memex" (1945). Other precursors were an early collaborative hypertext database called the ZOG (1972), and the Apple Computer hypertext system called HyperCard (1987).

However, the creation of the first wiki website only became possible with the development of the hypertext protocol of the WorldWideWeb (1991) and graphical web browsers such as the Netscape Navigator (1994). In order to facilitate communication between software developers, and also to experiment with the new hypertext capabilities, Ward Cunningham created the first wiki, which he called WikiWikiWeb (using the Hawaiian word "wiki" in place of "quick"). Cunningham went public with the first wiki in early 1995, inviting a selected group of programmers to participate in the experiment.

Ward Cunningham's first wiki met with immediate success, and quickly spawned "wiki clones," alternative versions of the wiki software. The use of wiki websites was rapidly adopted by communities of free software developers, but at first remained confined to these specialised groups. In the meantime the WikiWikiWeb evolved rapidly as features were added to the software and as the growing body of users developed a unique "wiki culture." By 2000 the number of contributors to Ward Cunningham's website had grown so large that conflicts developed between those who wanted to restrict the discussion to computer programming and those who wanted to discuss issues relating to the functioning of the wiki itself. The conflict was resolved by the creation the "SisterSites" MeatballWiki and WhyClublet as separate forums for discussion.

Wikis remained largely unknown outside of circles of software developers until around 2001, when the success of the free content encyclopedia Wikipedia introduced wikis to the general public. After 2001 the number of wiki websites and the varieties of wiki engines (software implementations) increased exponentially. There now exist thousands of wiki websites and hundreds of wiki engines.

Historical antecedents of the wiki concept

A distant precursor of the wiki concept was Vannevar Bush's vision of the "memex," a microfilm reader which would create automated links between documents. In his 1945 article How we may think, Vannevar Bush described how he imaged the future experience of the user: "Before him are the two items to be joined, projected onto adjacent viewing positions… The user taps a single key, and the items are permanently joined…. Thereafter, at any time, when one of these items is in view, the other can be instantly recalled merely by tapping a button below the corresponding code space. Moreover, when numerous items have been thus joined together to form a trail, they can be reviewed in turn…" This vision clearly foresees the hypertext mechanism, which will be taken advantage of by all wikis. However, hypertext is a general feature of all World Wide Web applications, rather than a feature that is specific to wikis. ^[1]

Another precursor of the wiki concept was the ZOG multi-user database system, developed in 1972 by researchers at Carnegie-Mellon University. The ZOG interface consisted of text-only frames, each containing a title, a description, a line with standard ZOG commands, and a set of selections (hypertext links) leading to other frames.

Two members of the ZOG team, Donald McCracken and Robert Akscyn, spun off a company from CMU in 1981 and developed an improved version of ZOG called Knowledge Management System (KMS). KMS was a collaborative tool based on direct manipulation, permitting users to modify the contents of frames, freely intermixing text, graphics and images, any of which could be linked to other frames. Because the database was distributed and accessible from any workstation on a network, changes became visible immediately to other users, enabling them to work concurrently on shared structures (documents, programs, ...). ^[2]

The ZOG system was the model for Janet Walker's Document Examiner, created in 1985 for the operation manuals of Symbolics computers. Document Examiner was in turn the model for the Note Cards system, released by Xerox in 1985. Note Cards is a hypertext system that features scrolling windows for each note card, combined with a separate browser and navigator window. Note Cards was the inspiration for Bill Atkinson's WildCard, which was later called HyperCard. ^[2] Ward Cunningham traces the wiki idea back to a HyperCard stack that he wrote in the late 1980's. ^[3]

The influence of Hyper Card on wiki inventor Ward Cunningham

Ward Cunningham was introduced to HyperCard (then called WildCard) by Kent Beck, who obtained access to it after joining Apple Computers. Cunningham used HyperCard to make a stack with three kinds of cards:

• cards for ideas,
• cards for people who hold ideas,
• cards for projects where people share ideas.

(One can recognise here the Patterns, People and Projects that are mentioned on the Front Page of Cunningham's original wiki, the WikiWikiWeb.) Cunningham made a single card that would serve for all uses. It had three fields: Name, Description and Links. The fields in HyperCard were WYSIWYG editors, but linking was a pain that involved moving between both cards. Cunningham abandoned regular stack links and used search-on-demand instead. Normally one would type links into the Links field. When using the card, each link had a button that would take you to the card if it existed, or beep otherwise. If you held the button down, it would relent and go make the card for you. (One can recognise here the traditional wiki feature by which a new page is opened for editing whenever one clicks on any new word formed in camel-case. In Wikipedia the equivalent feature is called "red links".) ^[4]

The WorldWideWeb sets the stage for the first wiki

Ward Cunningham's first wiki was made possible by the hypertext capabilities of the World Wide Web. In 1990 Tim Berners-Lee of CERN built the first hypertext browser, which he called WorldWideWeb (it was also a Web editor), and the first hypertext server (info.cern.ch). In 1991 he posted a short summary of the World Wide Web project on the alt.hypertext newsgroup, marking the debut of the Web as a publicly available service on the Internet.

Early adopters of the World Wide Web were primarily university-based scientific departments or physics laboratories. In May 1992 appeared ViolaWWW, a graphical browser providing features such as embedded graphics, scripting, and animation. However, the turning point for the World Wide Web was the introduction of the Mosaic graphical web browser in 1993, which gained wide popularity due to its strong support of integrated multimedia and the authors’ rapid response to user bug reports and recommendations for new features. Its creators formed Mosaic Communications Corporation, which changed its name to Netscape in April 1994, and the browser was developed further as Netscape Navigator. That same month CERN agreed that anyone could use the Web protocol and code for free. The stage was set for the appearance of Ward Cunningham's WikiWikiWeb.

The creation of WikiWikiWeb, the first wiki

Ward Cunningham started developing the WikiWikiWeb in 1994 as a supplement to the Portland Pattern Repository, a website containing documentation about Design Patterns, a particular approach to object-oriented programming. ^[3]

The WikiWikiWeb was intended as a collaborative database, dedicated to People, Projects and Patterns, ^[3] in order to make the exchange of ideas between programmers easier. Cunningham wrote the software to run it using the Perl programming language. ^[5] He named it using the alliterative Hawaiian word wiki-wiki, which means "quick-quick," to avoid calling it "quick-web". ^[3]

Cunningham installed a prototype of the software on his company Cunningham & Cunningham's website c2.com. In a surviving email received by Ward Cunningham on 6 November 1994, the server administrator Randy Bush wrote: "You will find the web stuff started and running, but rather content-free. It is in the directory /usr/local/etc/httpd/htdocs. You can send folk to … http://c2.com." Cunningham replied: "Actually, a higher priority for me is completing a first cut at my repository." ^[6]

A few months later, when the Repository was functioning, Cunningham sent to a colleague the following email, dated March 16, 1995:

Steve -- I've put up a new database on my web server and I'd like you to take a look. It's a web of people, projects and patterns accessed through a cgi-bin script. It has a forms based authoring capability that doesn't require familiarity with html. I'd be very pleased if you would get on and at least enter your name in RecentVisitors. I'm asking you because I think you might also add some interesting content. I'm going to advertise this a little more widely in a week or so. The URL is http://c2.com/cgi-bin/wiki. Thanks and best regards. – Ward ^[6]

Cunningham dates the official start of WikiWikiWeb as March 25, 1995. ^[3] On May 1, 1995 he sent to a number of programmers an InvitationToThePatternsList , which caused an increase in participation. ^[3] This note was posted to the “Patterns” listserv, a group of software developers gathered under the name "Hillside Group" to develop Erich Gamma's use of object-oriented patterns (inspired by Christopher Alexander's use of patterns in architecture). Cunningham had noticed that the older contents of the listserv tended to get buried under the more recent posts, and he proposed instead to collect ideas in a set of pages which would be collectively edited. Cunningham’s post stated: “The plan is to have interested parties write web pages about the People, Projects and Patterns that have changed the way they program." He added: "Think of it as a moderated list where anyone can be moderator and everything is archived. It's not quite a chat, still, conversation is possible." ^[7]

The site was immediately popular within the pattern community, due to both the newness of the World Wide Web and the good slate of invited authors. ^[3]

Initial WikiWiki software clones

Clones of the WikiWikiWeb software were soon developed. PatrickMueller wrote probably the first WikiWikiClone, using the RexxLanguage. ^[3] Ward Cunningham wrote a version of wiki that could host its own source code, called Wiki Base, and announced WikiWikiGoesPublic. The announcement said: "WikiWikiWeb is almost public. Actually, a pretty good clone of it is public at: http://c2.com/cgi/wikibase. I've translated almost all of the actual wiki script into HyperPerl, a wiki-literate programming system that I think you will like." Visitors were requested to register on the wiki before they took the Wiki Base code. ^[3]. Cunningham expected users to fold changes back into his editable version, but those who implemented changes generally chose to distribute the modified versions on their own sites. ^[3]

One of the early clones of Wiki Base was CvWiki, developed in 1997 by Peter Merel. CvWiki was the first Wiki Base clone to have functioning transclusion and backlinks. It was fully integrated with Concurrent Version System (CVS) software, thereby providing unlimited undo and no edit collisions. ^[8]

Initial wiki websites for software development

Inspired by the example of the WikiWikiWeb, programmers soon started several other wikis to build knowledge bases about programming topics. Wikis became popular in the free and open-source software (FOSS) community, where they were ideal for collaboratively discussing and documenting software, particularly given the loose structure of the projects. However, being used only by specialists, these early software-focused wikis failed to attract widespread public attention. ^[9]

Growth and innovations in WikiWikiWeb from 1995 to 2000

The WikiWikiWeb grew steadily from 1995 to 1998, and then snowballed between 1998 and 2000. Ward Cunningham's statistics about disk-usage show the following progression in the number of 1k blocks consumed by WikiWikiWeb pages: ^[3]

• Nov 29 1994: -
• Dec 15 1995: 2426
• Dec 1 1996: 5134
• Dec 31 1997: 10600
• Mar 25 1998: 14554
• Dec 2 2000: 62919

Some of the major innovations within WikiWikiWeb from 1995 to 2000, many of which were proposed by the community of users, were: ^[3]

• 1995 RecentVisitors, PeopleIndex: pages to help users know who was contributing
• 1995 NotSoRecentChanges: excess lines from the RecentChanges page were (manually) copied to a file of "ChangesIn<Month>"
• 1996 EditCopy: offers the possibility to edit the backup copy of a page (this was replaced in 2002 with Page History)
• 1996 ThreadMode: the form of a page where community members hold a discussion, each signing their own contribution
• 1996 WikiCategories: categories can be added as an automatic index to pages
• 1997 RoadMaps: proposed lists of pages to consult about specific topics, such as the Algorithms RoadMap or the Leadership RoadMap
• 1999 ChangeSummary: an aid to telling which changes added interesting new content and which were only minor
• 2000 UserName: the Wiki will accept a cookie that specifies a User Name to be used in place of the host name (IP identity) in the RecentChanges log

"ThreadMode" is defined as "a form of discussion where our community holds a conversation." It consists of a series of signed comments added down the page in chronological order. Ward Cunningham generally frowned on ThreadMode, writing: "Chronological is only one of many possible organizations of technical writing and rarely the best one at that." ^[10]

Cunningham encouraged contributors to "refactor" (rewrite) the ThreadMode discussions into DocumentMode discourse. In practice many pages started out at the top in DocumentMode and degenerated into ThreadMode further down. When ThreadMode becomes incomprehensible the result is called ThreadMess. ^[11] (On Wikipedia the conflict between these two modes has been resolved by putting all document text on the main page of an article, and all discussion text on the Talk page.)

The Categories were proposed by Stan Silver on August 27, 1996. ^[12] His initial post suggested: "If everyone adds a category and topic to their page, then the category and topic pages themselves can be used as automatic indexes into the pages." ^[13]

Ward Cunningham had originally created Wiki with the capability to click on the title of a page to see which pages pointed to it. Stan Silver used this reverse index technology to provide lists of the categories: ^[12] "Go to the CategoryCategory page and press its title to see all categories." ^[13]

Initially Stan Silver had proposed both categories and topics: categories denoted what the page was about (a book, a person, a pattern), while topics denoted the contents of the page (Java, extreme programming, Smalltalk). However, people ignored this separation, and so the topics were collapsed into the categories. ^[12]

The ChangeSummary began as an aid to telling which changes added interesting new content, and which were just minor adjustments of spelling, punctuation, or correction of web links. It started when some users began taking the RecentChanges page, annotating each line with a brief description of each change, and posting the result to the ChangeSummary page. This practice was highly time-consuming and rapidly petered out, but was replaced by the "MinorEdit/RecentEdits" feature, designed to reduce the RecentChanges clutter. (The ChangeSummary is the ancestor of the Wikipedia feature whereby an editor can enter a line of descriptive text when saving changes to a page.) ^[3]

Tensions within WikiWikiWeb and the creation of SisterSites

Between early 1998 and the end of 2000 participation in WikiWikiWeb snowballed, and the disk space consumed by wiki pages more than quadrupuled. With increased participation tensions began to appear.

In 1998 proponents of Extreme Programming showed up on the WikiWikiWeb and started posting comments about ExtremeProgramming on most of the pages related to software development. This annoyed a number people who wanted to talk about patterns, leading to the tag "XpFreeZone," which was put onto pages as a request not to talk about ExtremeProgramming on that page. Eventually most of the DesignPatterns people left to discuss patterns on their own wikis, and WikiWikiWeb was referred to as WardsWiki instead of the PortlandPatternRepository. ^[3]

Around the summer of 1999 a Wiki user known as SamGentile posted the comment "I'm through here" on his user page, and began systematically removing his text from all pages on WikiWikiWeb that he had contributed to. Sam Gentile worked at Microsoft and had been hurt by what he perceived as anti-Microsoft bias on WikiWikiWeb. His deletions led to controversy about whether he had the right to remove his own material, and whether others had the right to put it back in (which some began to do). This event became referred to as the WikiMindWipe, a term which would come to denote a general type of action, which in this particular case had taken the form of WikiSuicide. It was the first case of massive deliberate deletions of text on the WikiWikiWeb. It would be followed by another. ^[14]

On the morning of Friday 7th April 2000 four Europeans, Richard Drake, Keith Braithwaite, Stephan Houben and Manfred Schaefer, starting independently, tried to reduce the amount of text on Wiki by a large number of deletions. ^[15] They mainly attacked the "soft target" of WikiOnWiki material, which is defined as "Wiki pages devoted to Wiki, its nature, form and postulated future development." ^[16] They considered this material to be dead weight, and would have preferred to see it all replaced by concise guidance to newcomers. The primary focus of WikiWikiWeb was supposed to be on computer programming design patterns, and users who strayed too far from the focus were considered by some to be WikiSquatting, which meant developing their own separate community within the WikiWikiWeb.

The group that made the deletions became known as the WikiReductionists. The term has come to represent a general approach to Wiki editing, those advocating a contrary approach being called WikiConstructionists. ^[15] (On Wikipedia the equivalent terms are inclusionist and exclusionist, or deletionist.) ^[17][18]

Contributors who were outraged by the deletions of the WikiReductions began copying all of the deleted text back in again. A vote was taken of where the Wiki users stood on this issue. It was proposed that any "reductions" should be pre-announced, with an opportunity for response before action is taken. ^[15] (This was a distant precursor of the Wikipedia deletion policy, which requires announcement, discussion and voting before any controversial deletion of an article.)

Critics of the WikiReductionists accused them of escalating a flame war to the level of a ForestFire. ^[19] The longer-term result of the attack was the formation of WikiWikiWeb Sister Sites. In an amicable resolution to the conflict, Sunir Shah created MeatballWiki and invited all those who were interested in WikiOnWiki discussions to post their comments there. A few months later, Richard Drake (one of the four original WikiReductionists) created the WhyClublet (or "Why?") wiki to host discussion of Christian issues. Many pages were moved from WikiWikiWeb to these alternative sites, with a stub of the moved page left on the WikiWikiWeb, containing a link to the new page and the message: "This page exists only on SisterSites." The implementation of SisterSites at the level of changes to the Wiki script dates from 2001. ^[3]

In 2001 WikiWikiWeb founder Ward Cunningham and user Bo Leuf published a book, The Wiki Way, which distilled the lessons learned during the collective experience of the first wiki. ^[20]

The creation of Wikipedia

Until 2001 wikis were virtually unknown outside of the restricted circles of computer programmers. Wikis were introduced to the general public by the success of Wikipedia, a free content encyclopedia that can be edited by anyone.

Wikipedia was originally conceived as a complement to Nupedia, a free on-line encyclopedia founded by Jimmy Wales, with articles written by highly qualified contributors and evaluated by an elaborate peer review process. The writing of content for Nupedia proved to be extremely slow, with only 12 articles completed during the first year, despite a mailing-list of interested editors and the presence of a full-time editor-in-chief recruited by Wales, Larry Sanger. Learning of the wiki concept, Wales and Sanger decided to try creating a collaborative website to provide an additional source of rapidly-produced draft articles that could be polished for use on Nupedia.

Nupedia's editors and reviewers resisted the idea of associating Nupedia with a wiki-style website, so Wikipedia was launched on its own domain, wikipedia.com, on January 15 2001. It initially ran on UseModWiki software, with the original text stored in flat-files rather than in a database, and with articles named using the CamelCase convention UseModWiki was replaced by a PHP wiki engine in January 2002 and by MediaWiki in July 2002.

Wikipedia attracted new participants after being mentioned on the Slashdot website as well as in an article on the community-edited website Kuro5hin. It quickly overtook Nupedia. In the first year of its existence, over 20,000 encyclopedia entries were created, and the rate of growth has generally increased steadily since the inception of the project. As of 2007, Wikipedia includes several million freely-usable articles and pages in hundreds of languages worldwide, and content from millions of contributors. It is one of the most popular web sites and extensively used reference sites worldwide.

Trust and security

Controlling changes

Wikis are generally 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 time frame.^[7] Some wikis can filter the list to remove minor edits and edits made by automatic importing scripts ("bots").^[7]

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.^[7]

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 verify the validity of new editions quickly.^[7]

Trustworthiness

Critics of publicly-editable wiki systems argue that these systems could be easily tampered with, while proponents argue that the community of users can catch malicious content and correct it.^[1] Lars Aronsson, a data systems specialist, summarizes the controversy as follows:

Security

The open philosophy of most wikis, allowing anyone to edit content, does not ensure that all editors are well-meaning. Vandalism can be a major problem. In larger wiki sites, such as those run by the Wikimedia Foundation, vandalism can go unnoticed for a period of time. Wikis by their very nature are susceptible to intentional disruption, known as "trolling". Wikis tend to take a soft security^[9] approach to the problem of vandalism; making damage easy to undo rather than attempting to prevent damage. Larger wikis often employ sophisticated methods, such as bots that automatically identify and revert vandalism and JavaScript enhancements that show how many characters have been added in each edit. In this way vandalism can be limited to just "minor vandalism" or "sneaky vandalism", where the characters added/eliminated are so few that bots do not identify them and users do not pay much attention to them.

The amount of vandalism a wiki receives depends on how open the wiki is. For instance, some wikis allow unregistered users, identified by their IP addresses, to edit content, whilst others limit this function to just registered users. Most wikis allow IP editing,^{[citation needed]} but give registered users some additional editing functions; on most wikis, becoming a registered user is a short and simple process. Some wikis require an additional waiting period before gaining access to certain tools. For example, on the English Wikipedia, registered users can only rename pages if their account is at least four days old. Other wikis such as the Portuguese Wikipedia use an editing requirement instead of a time requirement, granting extra tools after the user has made a certain number of edits to prove their trustworthiness and usefulness as an editor. Basically, "closed up" wikis are more secure and reliable but grow slowly, whilst more open wikis grow at a steady rate but result in being an easy target for vandalism. A clear example of this would be that of Wikipedia and Citizendium. The first is extremely open, allowing anyone with a computer and internet access to edit it, making it grow rapidly, whilst the latter requires the users' real name and a biography of themselves, affecting the growth of the wiki but creating an almost "vandalism-free" ambiance.

Wiki software architecture

Wiki software is a type of collaborative software that runs a wiki system, allowing web pages to be created and edited using a common web browser. It is usually implemented as a software engine that runs on one or more web servers. The content is stored in a file system, and changes to the content are stored in a relational database management system. Alternatively, Personal wikis run as a standalone application on a single computer. Examples: WikidPad and VoodooPad.

Wiki communities

"WikiNode" redirects here, for the WikiNode of Wikipedia, see Wikipedia:WikiNode.

Many wiki communities are private, particularly within enterprises. They are often used as internal documentation for in-house systems and applications. The "open to everyone", all-encompassing nature of Wikipedia is a significant factor in its growth, while many other wikis are highly specialized.

There also exist WikiNodes which are pages on wikis that describe 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.

One way of finding a wiki on a specific subject is to follow the wiki-node network from wiki to wiki; another is to take a Wiki "bus tour," for example: Wikipedia's Tour Bus Stop. Domain names containing "wiki" 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. PeanutButterWiki, Socialtext, Wetpaint, and Wikia are popular examples of such services. For more information, see List of wiki farms. Note that free wiki farms generally contain advertising on every page. For those interested in how to build a successful wiki community, and encourage wiki use, Wikipatterns is a guide to the stages of wiki adoption and a collection of community-building and content-building strategies.

The English-language Wikipedia has the largest user base among all wikis^[10] and ranks in the top twenty among all websites in terms of traffic.^[11] Other large wikis include the WikiWikiWeb, Memory Alpha, Wikitravel, World66 and Susning.nu, a Swedish-language knowledge base. The largest wikis are listed and updated on Wikimedia's "meta" wiki.

Wikis and content management systems

Wikis have shared and encouraged several features with generalized content management systems (CMS), which are used by enterprises and communities-of-practice. Those looking to compare a CMS with an enterprise wiki should consider these basic features:

1. The name of an article is embedded in the hyperlink.
2. Articles can be created or edited at anytime by anyone (with certain limitations for protected articles).
3. Articles are editable through the web browser.
4. Each article provides one-click access to the history/versioning page, which also supports version differencing ("diff") and retrieving prior versions.
5. The most recent additions/modifications of articles can be monitored actively or passively.
6. Easy revert of changes is possible.

None of these are particular to a wiki, and some have developed independently. Still the concept of a wiki unequivocally refers to this core set of features. Taken together, they fit the generative nature of the Internet, in encouraging each user to help build it.^[12] It is yet to be studied whether an enterprise wiki encourages more usage, or leads to more knowledgeable community members, than other content management systems.