For Ward Cunningham father of the wiki, "a wiki is a freely expandable collection of interlinked Web 'pages', a hypertext system for storing and modifying information - a database, where each page is easily editable by any user with a forms-capable Web browser client" [1].

According to Wikipedia : "a wiki is a website whose users can add, modify, or delete its content via a web browser using a simplified markup language or a rich-text editor" [2].

You can watch the CommonCraft video"Wikis in Plain English" on YouTube to better understand what a wiki is.

The previous definitions show that a wiki is a "website," in other words it is composed of pages that are connected together by hyperlinks. In addition, every authorized person (not all wikis are totally open like Wikipedia) can edit the pages from a web browser, reducing time and space constraints. In case one saves a mistake, or for any other reason, would like to go back to a previous version, a feature called "history" allows users to see previous versions and to roll back to any of them. This version history allows a comparison of versions that avoids the clutter of the "commentaries rainbow" that we are used to in popular word processors. For example, if you work on a wiki page and come back later, you will be able to catch up by comparing your latest version with the lastest version generated by someone else.

Tools like Google Docs orEtherpad are design to enable co-editing on a single document. This can be seen as a "wiki way" of working on a document as it is web based and includes versioning. But it is not a wiki because a single document is not a website. Those tools offer realtime collaboration which wikis do not and are far easier for beginners to use as they work inWYSIWYG mode, which many wikis do not support. However, the advanced features of thewiki markup language make it a more powerful tool. In summary, tools like Googles Docs or Etherpad are a great way to quickly collaborate (synchronously, asynchronously, or a mixture of both) on a single document for free, with a low barrier to entry and no technical support. (Note that Etherpad does have a "wiki-links" plugin that can allow it to be used in a more wiki-like way; Hackpad is another real-time editing tool that prominently features linking -- and it claims to be "the best wiki ever".)

Using a real wiki engine is more interesting for bigger projects and allows a huge number of users to collaborate on the same platform. A wiki reduces the coordination complication as e-mails exchanges are no more needed to coordinate a project. On the other hand it can help us deal with complexity ([3], [4]) especially if you put basic simple rules in place like the Wikipedia'sneutral point of view to allow every participant to share her or his ideas.

Going back to the continuum we talked about before, some tools like Moodle, SharePoint, WordPress, Drupal and others have built-in wiki features. Those features can be good but will typically not be as good for wiki-building purposes as a well-developed special-purpose wiki engine. In other words, the main focus of those tools is not the wiki, which is only a secondary feature. When you choose a real wiki engine like Mediawiki,Tiki, Foswiki, etc., the wiki will be your platform, not a feature of it. For example if you start a wiki activity in a Moodle course, this wiki will be only visible to a specific group of students and searchable only to those students. On the other hand if your learning platform is a wiki, the whole platform will be searchable to all members regarding their permissions. We are not saying here that a wiki is better than other tools but if you need a wiki engine to address your needs you may consider going with a strong wiki engine rather than a "micro-wiki" engine embedded in an other tool.

Those are the main reasons you should consider a wiki for your peer learning projects :

• To reduce cumbersome coordination issues by having a central and continually updated place to store your content. You will reduce e-mail usage drastically, and have access to your content from anywhere, using any operating system.

• To keep track of the evolution of your project and be able to view or roll back any previous version of a wiki page using the history feature.

• To make links between wiki pages to connect ideas and people but also make links to external URL's. This last possibility is very handy to cite your sources.

• To deal with complexity. As a wiki allows anyone to contribute, if you set some easy rules like Wikipedia's NPOV (Neutral Point of View), you will be able to catch more complexity as you will allow everyone to express his or her opinion. Wikis also integrate a forum or comment feature that will help you solve editing conflicts.

• To deal with work in progress. A wiki is a great tool to capture an ongoing work.

• To support transparency by letting every member of the community see what all the others are doing.

• To support a network structure; as a wiki is in essence a horizontal tool.

Using a hyperlinks you can...

Gérard Ayache: "... jump by a single click from one network node to another, from one computer to another, from one bit of information to the other, from one universe to another, from one brain to another."  (Translated from [5].)

You will find more than a hundred different wiki engines.

The first main distinction is between open source ones that are free to download and commercial ones you will have to pay for. You will find powerful engines on both sides, both open-source and commercial. Sometimes, the open-source ones look less polished at first sight, but are backed by a strong community and offer a range of customization possibilities. The commercial wiki engines are sold as a package, nicely presented but often offering less customization on the user side. Additional features or custom-made tools will cost you extra.

The second distinction that we can make is between wiki farms and self-hosted wikis. Thewiki farm is a hosting service you can find for both open-source or commercial wikis. The goal of those farms is to simplify the hosting of individual wikis. If you don't want to choose wiki farm hosting, you will have to host the wiki on your own server. This will give you more latitude and data privacy but will require more technical skills and maintenance fees.

The Wikimatrix web site will help you choose the best wiki for your needs. It allows you to compare the features of more than a hundred wiki engines. Ward Cunningham's list of the top 10 best wiki engines can be found on ourPeeragogy.org site.

A wiki is a good tool for collaborative projects and especially suited for work in progress, as you can easily track changes using the history, compare those versions and, if necessary, roll back to previous versions. In other words, nothing gets lost.

Here are some ideas about how to use a wiki in a peeragogy project :

• Use a wiki as your learning platform. It can also support Massive Open Online Courses (MOOCs). A wiki will help you organize your learning context. You can choose to give access to your wiki only to the project participants or open it to the public like Wikipedia. Using hyperlinking, you will operationalize the theory of connectivism by connecting nodes together. As a learning platform, wikis are powerful because you can easily see what others are doing, share with them, get inspired, merge ideas or link to ideas. In other words, it fosters emulation between learners. For additional resources about wikis in education, look on Diigo.

• Manage your peeragogy project. A wiki is an excellent tool for project collaboration. Above all, the wiki can be a central place for peer learners to write or link to content. Even if you use several technologies to run your project as we did to write this handbook, at the end of the day all the content can be centralized on a wiki using direct writing on wiki pages or embedding hyperlinks. This way, members can access the content from anywhere and from any device connected to the internet, using any platform or application. They will always see the most recent version while being able to browse through the version history to understand what has changed since their last visit.

• Publish your project. As a wiki is a website you can easily use it to show your work to the world. Regarding web design, don't forget that a wiki can look way better than a Wikipedia page if you customize it

Appropedia is a wiki site for collaborative solutions in sustainability, poverty reduction and international development through the use of sound principles and appropriate technology and the sharing of wisdom andproject information. The site is open to stakeholders to find, create and improve scalable and adaptable solutions.

Teahouse is a peeragogy project run on a wiki that gives newcomers a place to learn about Wikipedia culture and get feedback from experienced Wikipedians.

• *Cofacilitation* -- help each other learn, help each other administer

• *Self-election* -- enable people to choose what they want to work on, at their own pace, in their own way

• *Communication* -- use comment threads and talk pages to discuss wiki changes

• *Documenting changes* -- most wikis enable editors to write very brief descriptions of their edits

• *Rules* -- keep rules at a minimum level to avoid chaos without constraining creativity

• *Fun* -- make it fun for people to contribute

• Check path in the script

• Install _firn directory

• print working directory

• List contents

• Set site-url in config.edn

1. Leuf, Bo, et Ward, Cunningham. 2001. The Wiki way : quick collaboration on the Web. Boston: Addison-Wesley, xxiii, 435 p. p.14

2. Wiki on Wikipedia

3. Andrus, Calvin D. 2005. Toward a complex adaptative intelligence community - The wiki and the blog. Studies in Intelligence. vol. 49, no 3. Online :

4. Barondeau, Régis. 2010. La gestion de projet croise le wiki. École des Sciences de la Gestion, Université du Québec à Montréal, 180 pp.

5. Ayache, Gérard. 2008. Homo sapiens 2.0 : introduction à une histoire naturelle de l'hyperinformation. Paris: Milo, 284 p. p.179