So, what is a wiki?
A wiki is a website where all users have the option of editing the content. It is a very simple concept; while many of the current implementations contain many extra functions, the basic idea of a simple interface that a non-technical person can quickly learn, use and remember is the core feature in most wikis.
At a minimum, a wiki only needs a very small number of features to be useful. These include the ability to create and edit pages directly via a web browser, a page history which allows changes to be rolled back and a list of recently changed pages. A search option and information about the authors of each page are the final two features for any simple wiki.
In practice, most wikis have many more features than this small set. For instance, some wikis, such as MediaWiki (which is used for Wikipedia), are specifically built for public internet sites. Another subset of wikis can be categorised as enterprise wikis. Enterprise wikis are aimed at corporations that have a typical, modern information technology infrastructure that might contain items such as an LDAP-based user administration facility, separate database installations that are backed up and highly reliable or a departmental structure that will require certain parts of the wiki to have protected access. Enterprise wiki implementations have the basic wiki features noted above plus an additional set of features that are required for working in an enterprise environment. These features will include such features as LDAP or database connectivity, fine-grained page security, the ability to create sub-spaces within the wiki, a full search including an attachment search and finally a slick interface.
Many commercial wikis now support most, or all, of these enterprise features while some open-source wikis, especially TWiki, support many of these features, too. Confluence and Twiki are two wiki implementations that are readily extensible. Both have active communities which have developed hundreds of plug-ins. Some so-called structured wikis are extendable with plug-ins that add many hundreds of additional features.
As of mid 2007, there were more than 80 different wiki implementations available, many of them free and open source. A useful tool to help sort them out is the popular wikimatrix site. Wikimatrix tracks about 150 different features in its comparison of major wikis. A good article about the future of wikis and where they are taking us is "Wired Wiki", published by Wired Magazine. The article itself was created as a wiki and you can read the full text at the Wired Wiki page.
