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MediaWiki

Web Design & Development Guide

MediaWiki

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MediaWiki
MediaWiki logo

The Main Page of the English Wikipedia.
Maintainer: Wikimedia Foundation
Stable release: 1.10.1  (July 13, 2007) [+/-]
Preview release: -  (-) [+/-]
OS: Cross-platform
Use: Wiki
License: GNU General Public License
Website: http://www.mediawiki.org/

MediaWiki is a web-based wiki software application used by all projects of the Wikimedia Foundation, all wikis hosted by Wikia, and many other wikis, including some of the largest and most popular ones.[1] Originally developed to serve the needs of the free content Wikipedia encyclopedia, today it has also been deployed by companies as an internal knowledge management solution, and as a content management system. Notably, Novell uses it to operate several of its high traffic websites.[2]

MediaWiki is written in the PHP programming language, and can use either the MySQL or PostgreSQL relational database management system. Distributed under the terms of the GNU General Public License, MediaWiki is free software.

History

The current software was originally written for Wikipedia by Lee Daniel Crocker, based on the user interface design of German University of Cologne student and developer Magnus Manske. Wikipedia had originally used a small wiki engine called UseModWiki written in Perl. Wikipedia was later switched to Manske's PHP-based software to offer more functionality. Increasing usage caused load problems, leading Crocker to re-write the software with a more scalable MySQL database backend. Later, Brion Vibber would take up the role of release manager and most active developer.[3]

Since the release of the first version of Manske's script, the software had been given multiple nicknames representing the state of development—"the PHP script", "phase II", "phase III", "the new codebase"—but no product name. After the Wikimedia Foundation was announced on June 20, 2003, the name "MediaWiki" was coined by Wikipedia contributor Daniel Mayer as a play on "Wikimedia," [4] and the name was gradually phased in beginning in August 2003. The name has frequently caused confusion due to its intentional similarity to the "Wikimedia" name (which itself is similar to "Wikipedia"). Nevertheless, "MediaWiki" has become a recognizable brand, with a Google search yielding over 178 million results on the name in July 2007.

The product logo was created by Erik Moeller using a flower photograph taken by Florence Nibart-Devouard, and was originally submitted to an international logo contest for a new Wikipedia logo held in summer 2003.[5] The logo came in third place, and was chosen to represent MediaWiki instead of Wikipedia, with the second place logo used for the Wikimedia Foundation and the first place logo for Wikipedia itself.[6] The double square brackets around the photo of a sunflower symbolize the syntax MediaWiki uses for creating hyperlinks to other wiki pages.

Release history

Version number Date Notable changes
1.1[7] December 8, 2003
  • New wiki table syntax.
  • User-editable interface messages through "MediaWiki namespace".
  • XML-wrapped page source export with optional history.
  • "Magic words" - special variables and parser instructions.
1.2[8] March 24, 2004
  • Experimental web-based installer.
  • Image resizing and thumbnail generation.
  • Editing toolbar for learning wiki syntax.
  • User rights management within the wiki.
1.3[9] August 11, 2004
  • New, highly CSS-based default look and feel ("MonoBook" skin) and better web standards compliance.
  • Parametrized templates.
  • Category feature.
  • Automatic merging of edit conflicts when possible.
  • Improved installation.
1.4[10] March 20, 2005
  • User interface language can be changed by the user.
  • Significant performance improvements.
  • Support for compressing old revisions of articles to reduce storage needs.
  • Image gallery generation, list of recently uploaded images.
  • SVG rasterization support (requires external support tools).
1.5[11] October 5, 2005
  • Major database redesign decoupling text storage from revision tracking, resulting in:
    • Significant performance boosts for some operations.
    • Permalink functionality for all revisions.
    • Support for storing bulk data outside the database.
  • Support for e-mail notification upon changes.
  • Page content must be encoded in UTF-8.
1.6[12] April 5, 2006
  • The account creation form has been separated from the user login form.
  • Page protection/unprotection uses a new, expanded form.
  • "Job queue" for background updates.
  • Improved tracking of template usage.
  • Tracking of external link usage for more systematic anti-spam measures.
  • Template parameters can have default values.
1.7[13] July 7, 2006
  • MediaWiki 1.7 requires PHP 5 (5.1 recommended). PHP 4 is no longer supported.
  • Deleted files can now be restored.
1.8[14] October 10, 2006
  • Full support for PostgreSQL (8.1 or better) database backend
  • Support for DjVu thumbnailing and multipage navigation
  • Various improvements to user blocking; blocks can be placed only on unregistered users using a particular IP address
  • Uploading files from publicly accessible URLs is possible if enabled
1.9[15] January 10, 2007
  • "Undo revision" feature
  • Various improvements to blocking and special page caching
  • Tables with sortable columns
  • Addition of an edit counter field to the user database
  • Revision size displayed on watchlists and recent changes
1.10[16] May 9, 2007
  • "Cascading protection" feature
  • Improved tooltips and accesskey feature
  • Various improvements to blocking and special page caching
  • IPv6 support

Key features

Editing interface of MediaWiki 1.7 as rendered in Firefox, showing the edit toolbar and some examples of wiki syntax.
Editing interface of MediaWiki 1.7 as rendered in Firefox, showing the edit toolbar and some examples of wiki syntax.

MediaWiki provides a rich core feature set and a mechanism to attach extensions to provide additional functionality. Due to the strong emphasis on multilinguality in the Wikimedia projects, internationalization has received significant attention by developers. The user interface has been fully or partially translated into more than 70 languages, and can be further customized by site administrators (the entire interface is editable through the wiki). Because Wikipedia is one of the world's largest websites, achieving scalability through multiple layers of caching and database replication has also been a major concern for developers. Wikipedia and other Wikimedia projects continue to define a large part of the requirement set for MediaWiki.

One of the earliest differences between MediaWiki (and its predecessor, UseModWiki) and other wiki engines was the use of "free links" instead of CamelCase. Where, in a typical wiki, text like "WorldWideWeb" would have to be typed to create a link to a page about the World Wide Web, links in MediaWiki are created by surrounding words with double square brackets, and any spaces between them are left intact, e.g. [[World Wide Web]]. This change was logical for the purpose of creating an encyclopedia, where accuracy in titles is very important.

To make editing long pages such as comprehensive Wikipedia articles easier, MediaWiki supports editing only a small subsection of a page (as identified by its header).

Rich content

Images can be arranged in galleries, a feature that is used extensively for Wikimedia's media archive, Wikimedia Commons.
Images can be arranged in galleries, a feature that is used extensively for Wikimedia's media archive, Wikimedia Commons.

MediaWiki supports rich content generated through specialized syntax. For example, the software comes with support for rendering mathematical formulas using LaTeX and a special parser written in OCaml. Similar functionality for other content, ranging from graphical timelines over mathematical plotting and musical scores to Egyptian hieroglyphs, is available in the form of extensions.

As the name MediaWiki suggests, the software has become ever more powerful at dealing with a wide variety of uploaded media files. Its richest functionality is in the area of images, where image galleries and thumbnails can be generated with relative ease if the software is set up correctly. There is also support for Exif metadata. The use of MediaWiki to operate the Wikimedia Commons, one of the largest free content media archives, has driven the need for further functionality in this area.

MediaWiki currently provides no native WYSIWYG support, though it does come with a graphical toolbar for simplifying the process of learning the wiki syntax. It also has a simple interface to allow the transparent use of external editors for uploaded files and wiki pages.

Organization

MediaWiki provides many features beyond hyperlinks for structuring content. One of the earliest features is namespaces. One problem for Wikipedia had long been the separation of encyclopedic content from discussions surrounding it, as well as personal pages about encyclopedia editors. Namespaces are prefixes before a page title (like "User:" or "Talk:") which allow a page to exist under multiple names, but serving different purposes depending on their prefix. For instance, a page "[[The Terminator]]" could describe the 1984 movie starring Arnold Schwarzenegger, while a page "[[User:The Terminator]]" could be a profile describing a user who chooses this name as a pseudonym. More commonly, each page has an associated "Talk:" page which can be used to discuss its contents.

Namespaces can be viewed as folders which separate different basic types of information or functionality. While new namespaces can be added, the number of namespaces in a wiki is typically relatively low.

In addition to namespaces, pages can be structured using subpages. This simple feature provides automatic backlinks from a page of the pattern [[Page title/Subpage title]] to the component before the slash (in this case, "Page title").

MediaWiki supports user-created categories. These are similar to tags used in many web applications, but hierarchical and descriptive. In large wikis like Wikipedia, very complex hierarchies have grown using this system without any central planning.[17]

Customisation

Users can configure custom JavaScript that is executed on every pageview. This has led to JavaScript tools that users can "install", the "navigation popup" tool shown here displays a small preview of an article when hovering over a link title.
Users can configure custom JavaScript that is executed on every pageview. This has led to JavaScript tools that users can "install", the "navigation popup" tool shown here displays a small preview of an article when hovering over a link title.

If the feature is enabled, users can customize their stylesheets and configure client-side JavaScript to be executed with every pageview. On Wikipedia, this has led to a large number of additional tools and helpers developed through the wiki and shared among users. For instance, Lupin's navigation popups is a custom JavaScript tool that shows previews of articles when the user hovers over links, and also provides shortcuts for common maintenance tasks.[18] Another example is wikEd, a full-featured MediaWiki-integrated text editor that provides syntax highlighting and search and replace functions. [19]

The entire MediaWiki user interface can be edited through the wiki itself by users with the necessary permissions (typically so-called "administrators"). This is done through a special namespace with the prefix "MediaWiki:", where each page title identifies a particular user interface message. The "MediaWiki:" namespace was also originally used for creating custom text blocks that could then be dynamically loaded into other pages using a special syntax. This content was later moved into its own namespace, "Template:".

Templates are text blocks which can be dynamically loaded inside another page whenever that page is requested. The template "tag" is simply a special link in double curly brackets (for example "{{disputed}}") which calls the template (in this case located at Template:Disputed) to load where the tag is. Templates support parameters, so that parts of the text can be substituted for each specific use case. A related method, called template substitution (called by adding subst: at the beginning of a template tag) inserts (like a copy and paste operation) the contents of the template into the target page, instead of loading the template contents dynamically whenever the page is loaded. This limits the consistency of using templates, but may be useful in certain cases, and is (perhaps) less demanding on the server.

Templates have found many different uses, such as:

  • Identifying problems with a Wikipedia article by putting a template in the article. This template will then output a graphical box stating that the article is disputed, and also categorize it so that articles of this nature can be located.
  • Creating complex table layouts which are used consistently across multiple pages, and where only the content of the tables gets inserted using template parameters.
  • Sending users standard messages when they are blocked from editing, when their behavior is considered inappropriate, and so on.
The Semantic MediaWiki extension
The Semantic MediaWiki extension

MediaWiki has the user interface in different languages. A language for the wiki content itself can also be set, but multilingual wiki content is not supported, i.e. one cannot choose the ISO 639 code mul for multilingual content.

The MediaWiki codebase contains various "hooks" where additional code can be attached. This allows programmers to write extensions without modifying the core or having to submit their code for review. Installing an extension typically consists of adding a line to the configuration file, though in some cases additional changes such as database updates are required.

Many of the available extensions are simple scripts to allow embedding content such as Adobe Flash files or HTML forms. Others add complex new behavior to the wiki syntax, such as Semantic MediaWiki which provides the ability to add structured and searchable relations and attributes to wiki pages (cf. semantic web). The Wikimedia Foundation operates a Subversion server where many extensions are hosted, and a directory of them can be found on the MediaWiki website.[20]

Access and groups

While MediaWiki comes with a basic set of features related to restricting access and defining user groups, page access control does not tend to be given high priority in development. For instance, it is not possible to define the access permissions to pages on a per-namespace basis. Here, wikis like TWiki and MoinMoin provide more power by supporting advanced security mechanisms like Access Control Lists.

Performance

Because it is used to run one of the highest traffic sites on the World Wide Web, Wikipedia, MediaWiki performance and scalability have been highly optimized. MediaWiki supports Squid caches, load balanced database replication, client-side caching, memcached or table-based caching for frequently accessed processing or query results, a simple static file cache, feature-reduced operation, revision compression, and a job queue for database operations.

MediaWiki may be overdimensioned for small-scale usage, where its large feature set and use of a database backend take a performance toll. On the other hand, the software is suitable for the operation of large scale wiki farms, such as the Wikimedia project and language family. However, MediaWiki comes with no built-in functionality to manage such installations.

Limitations

Aside from the aforementioned lack of WYSIWYG features, user documentation is found online only (there is no printed manual) and is not proprietary (dozens of authors have contributed to the documentation). The installation and usage of the Mediawiki software is not intuitive for inexperienced computer users (compared to purpose made software such as FrontPage for example).

There is no complete MediaWiki syntax definition — the syntax is defined by the parser PHP code, and an Extended Backus–Naur form (EBNF) syntax definition may not be possible. This has caused difficulties in creating a WYSIWYG editor or complete ports of the parser to other languages.

Furthermore, there is no offline version of MediaWiki, which would enable users to update pages on their client offline, and then have those pages automatically transferred to the server when re-connected, in a similar way to the client-server operation of Lotus Notes. An offline MediaWiki client could also help users with the back-up of important pages.

Table operations could be improved. While the syntax for creating tables is not difficult for most IT-literate people to learn, it is offputting for the wider audience of subject-matter experts that Wikipedia would want to update its pages. Adding and removing columns from a table is tedious for all users. Calculations on data in table cells are also time-consuming to set up, compared to any spreadsheet.

See also

References

External links


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