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MediaWiki is a free-software open-source package written in PHP and originally for use on Wikipedia as Wiki engine. It has been licensed under the GNU General Public License.

A Wiki is a Website that allows the creation and editing of any number of interlinked Web pages via a Web browser using a simplified markup language or a WYSIWYG text editor. The first Wiki (titled WikiWikiWeb) was developed by Ward Cunningham in 1994.

The Wikipedia is the largest and most famous MediaWiki site.

0.1 Possibilities

Ward Cunningham comments that the main characteristics of a Wiki are:

1. Users can create Wiki pages or modify existing ones by means of a plain Web browser. An user can be everyone that have access to the Web server where the Wiki pages are stored. Usually, users are required to register in order to have editing capabilities (although this is optional).
2. Users can collaborate in the task of developing the Wiki pages and no hierarchy nor priorities between users are defined. In this sense, a Wiki is (by default) completely open to everybody that have something to say related to the Wiki’s matter.
3. Every modification in the Wiki is registered and traced. By means of this characteristic, it is possible to know who has performed an action and when. User registering can be mandatory in some Wiki sites for this reason.
4. The massive collaborating possibilities of a Wiki can produce excellent document resources in a record time. Therefore, some people have compared the Wiki pages to “living organisms” that evolves and adapt to the requirements of the Wiki users.

Lets check if these possibilities are true!

0.2 Installation and basic configuration

0.3 Removing MediaWiki

If during the installation something was wrong, you can erase the installation of the previous packages and re-install them. Just try:

0.4 How do I access to the Wiki site?

In general, Wikis can be read and modified by any Web surfer. The only thing you really need is the URL of the Wiki. In our example:

You should know that some Wiki administrators configure their sites in a way that only those users than are registered can modify the contents of the pages. In any case, user registering and log-in is important to record the activity of the users in the Wiki. Typically, no special requirements such as valid e-mail addresses will be required.

0.5 How do I create a new page?

When the MediaWiki engine has been installed and configured, an user can create a new page using two ways:

1. Specifying a new URL in the Wiki site. For example, after the installation of MediaWiki in our host, if we browse http://localhost/mediawiki we will automatically redirected to http://localhost/mediawiki/index.php/Main_Page. If we change “Main_Page” by whatever other string, we will created a new Wiki page after clicking on the “create” link.
2. Defining in the current page a new link to the page that we want to create and then clicking on the red link which appears.

0.6 Page structure

Although Wiki pages are fully configurable, by default, there are two main versions of a page:

1. The Page (or Article) version that usually has the “definitive” content.
2. The Discussion version in which users talk about the contents of The Page. This is similar to an off-line chat.

For each of the two versions of the page, there are four actions (or links) that can be followed:

1. Edit: to edit the page.
2. History: to see a different version of the page and who has created that version.
3. Move: to change the URL of the page.
4. Watch-list: to label this page as “watchable”. This means that if the page is modified, an e-mail will be sent to the user.

0.7 Page syntax

The Wiki pages are written in a lightweight markup language typically known as Wikitext language or Wiki Markup, although LaTeX code can be inlined for defining the formulas. Their ultimate purpose is to be converted by the Wiki engine into HTML, which is the language that understand Web browsers.

The next subsections show how to create the content a Wiki page. Obviously, we need first a empty page. Please, create a new page following the instructions given in Subsection 0.5.

Writing plain text

Defining subsections, paragraphs and so on ...

Bold and italics

Mathematics As you can see in the Wiki editor, it is possible to write mathematical expressions using the LaTeX syntax. In order to do this, you have to install:

and verify that the line $wgUseTeX = true; is in /etc/mediawiki/LocalSettings.php, obviously uncommented.

Once this is done, try to introduce in your Wiki page the following code:

Links between Wiki pages in the same server Create a new Wiki page called new_page_2. Return to the previous one and write in it:

Save the changes and a link from the first page to the second one will appear.

Links to other Web pages

Verbatim text

Indentations

Bullet pointed items

Enumerated items

0.8 User access levels

The status of a user in a MediaWiki server depends on the number of identification stages that the user has performed in that server. These are the possibilities:

1. Unregistered: Those users that are not logged in the Wikipedia.
2. Logged in: Those users that have created an account and logged in.
3. Autoconfirmed: Those users that have an account with more than four days old and have made at least 10 edits.
4. Confirmed: Those users that have an account and have been confirmed by the Wiki administrator.

In some Wiki sites such as the Wikipedia only the autoconfirmed and confirmed users can modify the contents.

0.9 Dealing with audio, image and video

Wiki pages that are served by any MediaWiki engine can reference multimedia content. All multimedia files have to be stored in a MediaWiki server (for example, the images, sounds and videos used in the Wikipedia are stored in the Wikimedia Commons online repository).

Uploading a new media file File uploading in our local host MediaWiki server is performed through the URL:

Only logged in users are capable of upload media files. Anyway, if you tray it and get a “File uploads are disabled” error, the Web server administrator have to enable file uploading first (see Subsection 0.9). Otherwise, a Web form will allow you to upload a file to the server.

Enabling file uploading By default, file uploading to a new MediaWiki server maybe is disabled. To enable it, as Web server administrator, the following actions have to be performed:

1. Make sure uploads are enabled in PHP. In our server (under Ubuntu), check that the file
   /etc/php5/cli/php.ini

   has the line file_uploads = On uncommented and that the file

   /usr/share/mediawiki/LocalSettings.php

   has the line $wgEnableUploads=true inside it, obviously uncommented too.

By default, only the extensions .png, .gif, .jpg and .jpeg are allowed for the uploads (and, as you can see, all of them are image containers). If you need to support different media data, such as audio or video, you have to modify the content of the $wgFileExtensions in the file LocalSettings.php. For example, if you write:

.avi and .ogg files will be supported also.

At any case, notice that your Web browser must support this kind of media data and containers if you want to reproduce it.

Listing previously uploaded images It is possible to watch what media files are stored on your server using the URL:

Referencing media files For example, to reference the image Lena.png what has been previously uploaded to the Wiki server, we can write in the Wiki page:

0.10 Protecting pages

Some Wiki pages need some kind of protection against vandalism. The MediaWiki administrator can protect a page to restrict editing or moving that page, and of course, remove such restriction. Protection can be indefinite, or expire after a specified time. When you are logged in the Wiki site as administrator, the “protect” link is available for every page you visit.

Notice also that there are two levels of protection:

1. Full protection: a fully protected page can be edited only by administrators.
2. Semi-protection: semi-protected pages can be edited only by registered users that have been confirmed.

0.11 Resolving conflicts

Wiki pages can be edited currently by several users. Therefore, an edit conflict could arise in the following situation:

1. User-1 edits page X.
2. User-2 edits the same page X.
3. User-1, after modifying the page, “saves” the page.
4. User-2, after modifying the page, try to save it but the system says to User-2 that he has an “edit conflict” because the Automatic Conflict Resolver¹ can not merge his changes with the User-1’s ones.

In this points, there are two solutions:

1. User-2 reloads the actual version of the page X (those that User-1 has just generated) and extremely fast makes the modifications that he want and save it. Obviously, this is not a useful solution!
2. User-2 uses a conflict page to reconcile the differences between his version of the page and the User-1’s one. Again, it is only responsibility of the User-2 the resolution of his conflicts.

As you can deduce, it is very recommendable that users that are editing a page perform the saving-and-reload operation of that page several times, basically after any minor edition, in order to make easier the work of the automatic conflict resolver.