free, Internet-based encyclopaedia operating under an open-source (open source) management style. It is overseen by the nonprofit Wikimedia Foundation. Wikipedia uses a collaborative software known as wiki that facilitates the creation and development of articles. The English-language version of Wikipedia began in 2001. It had more than one million articles by March 2006 and more than two million by September 2007, and it continues to grow at a rate of millions of words per month. Much of its content treats popular culture topics not covered by traditional encyclopaedias. Wikipedia is also an international project with versions in scores of languages, including French, German, Polish, Dutch, Hebrew, Chinese, and Esperanto. Although some highly publicized problems have called attention to Wikipedia's editorial process, they have done little to dampen public use of the resource.

In 1996 Jimmy Wales (Wales, Jimmy), a successful bond trader, moved to San Diego, Calif., to establish Bomis, Inc., a Web portal company. In March 2000 Wales founded Nupedia, a free online encyclopaedia, with Larry Sanger as editor-in-chief. Nupedia was organized like existing encyclopaedias, with an advisory board of experts and a lengthy review process. By January 2001, fewer than two dozen articles were finished, and Sanger advocated supplementing Nupedia with an open-source encyclopaedia. On Jan. 15, 2001, Wikipedia was launched as a feature of Nupedia.com, but, following objections from the advisory board, it was relaunched as an independent Web site a few days later. In its first year, Wikipedia expanded to some 20,000 articles in 18 languages. In 2003 Nupedia was terminated and its articles moved into Wikipedia.

In some respects, Wikipedia's open-source production model is the epitome of the so-called Web 2.0, an egalitarian environment where the web of social software enmeshes users in both their real and virtual-reality workplaces. The Wikipedia community is based on a limited number of standard principles. One important principle is neutrality; another is the faith that contributors are participating in a sincere and deliberate fashion. Readers can correct what they perceive to be errors, and disputes over facts and possible bias are conducted through contributor discussions, with Wales as the final arbiter. Three other “pillars of wisdom” are: not to use copyrighted material, not to contribute original research, and not to have any other rules. The last pillar reinforces the project's belief that the open-source process will make Wikipedia into the best product available, given its community of users.

The central policy of inviting readers to serve as authors or editors creates the potential for problems as well as their partial solution. Not all users are scrupulous about providing accurate information, and Wikipedia must also deal with individuals who deliberately deface particular articles, post misleading or false statements, or add obscene material. Wikipedia's method is to rely on its users to monitor and clean up its articles. Trusted contributors can also receive administrator privileges that provide access to an array of software tools to fix Web graffiti and other serious problems speedily.

Reliance on community self-policing has generated some problems. In 2005 the American journalist John Seigenthaler, Sr., discovered that his Wikipedia biography falsely identified him as a potential conspirator in the assassinations of both John F. Kennedy and Robert F. Kennedy and that these malicious claims had survived Wikipedia's community policing for 132 days. The author of this information could not be easily identified, since all that is known about contributors is their computers' IP, or Internet protocol, addresses (many of which are dynamically generated each time a user goes online). (The contributor later confessed and apologized, saying that he wrote the false information as a joke.) Wikipedia administrators have the power to block particular IP addresses—a power they used in 2006 after it was found that staff members of some U.S. congressional representatives had altered articles to eliminate unfavourable information.

News of such self-interested editing inspired Virgil Griffith, a graduate student at the California Institute of Technology, to create Wikipedia Scanner, or WikiScanner, in 2007. By first downloading the entire Wikipedia corpus, Griffith was able to view all of the edits made to its articles and the IP addresses where the edits originated. He then correlated these addresses with their owners (individuals, corporations, and government entities) to create a database that he made available on the Web for anyone to search through. He and other researchers quickly discovered that editing from computers located in corporations and government offices was widespread. Although most of the edits were innocuous—typically, individuals working on subjects unrelated to their positions—a pattern did seem to emerge of many articles being edited to reflect more favourably on the editors' hosts. Articles on political subjects in particular have become the greatest test of Wikipedia's principle of neutrality. To help on this front, Griffith released another tool, WikiGanda, in 2008. The new database documents some of the site's “edit wars,” or propaganda battles, such as the intermittent efforts of neo-Nazis to rewrite Wikipedia's articles on the Holocaust.

For many observers of these controversies, a troubling difference between Wikipedia and other encyclopaedias lies in the absence of editors and authors who will accept responsibility for the accuracy and quality of their articles. These observers point out that identifiable individuals are far easier to hold accountable for mistakes, bias, and bad writing than is a community of anonymous volunteers, but other observers respond that it is not entirely clear if there is a substantial difference. Regardless of such controversies—perhaps in part because of them—Wikipedia has become a model of what the collaborative Internet community can and cannot do.