Now that you possess the skills to program all three types of extensions (modules, components, and plug-ins), your development will probably require that you integrate any extension you create with the Joomla system. This means understanding how Joomla functions on an execution level, and likely being able to make calls to the Joomla framework.

 The complete Joomla framework is divided into a sizable number of packages, most of which are represented in an actual Joomla installation with a folder dedicated to the source files:

❑       Application Package — JApplication and related libraries are implemented as a factory class. The four classes extended from this package (JInstallation, JModel, JSite, and JAdministrator) make up the Joomla CMS application. Also included are the Data Access Object (DAO) libraries, including the abstract JModel class that is extended to create the classes JModelCategory, JModelComponent, JModelMenu, JModelModule, JModelPlugins, JModelSection, JModelSession, and JModelUser. It is located in the librariesjoomla directory.

Unlike modules that are all stored in the modules folder or components that all exist in the components folder, plug-ins are categorized and grouped within folders that define their categories. For example, plug-ins that provide search functionality are stored in the pluginssearch folder, while content plug-ins exist in the pluginscontent folder.

In the Plugin Manager, the category of plug-in is generally displayed in two places: as a prefix to the plug-in name and in the Type column. The name of each plug-in is preceded by the type. For example, the LDAP plug-in displays a name of “Authentication - LDAP.” The type of plug-in defines how the extension will be treated by the system.

The eight different types of plug-ins include the following:

In the 1980s, Ward Cunningham invented a new method of collaboration called a wiki, which is a Web site where visitors can add, edit, supplement, and remove articles from an encyclopedic store. The most famous example is an online encyclopedia known as Wikipedia (www.wikipedia.org). Users of the Web site have created or contributed to more than 2 million articles currently featured there.

Within the last decade, there has been incredible growth in the wiki phenomenon, especially related to technology. The open source community, in particular, benefits from the wiki Web sites, since many of the programmers of open source applications often lack the time to document their work. A wiki created to feature a particular application (such as the FreeMind mind-mapping tool) allows passionate users to add useful information, tips, and document parts of the program that aren’t self-explanatory.

Joomla is capable of hosting a wiki system through a component known as OpenWiki. OpenWiki is an extension adapted from the open source DokuWiki project (created by Andreas Gohr), which is a PHP application that provides wiki capabilities. OpenWiki is made to be fast and light, so while other wiki applications may include more features (such as the open source MediaWiki that is used for Wikipedia), OpenWiki consumes much fewer resources and provides much more responsiveness.

Podcasting is the new media. A recent Bridge Ratings study indicated that the number of people who downloaded a podcast has risen from 820,000 in 2004 to 4.8 million people in 2005. Projections for audience growth by 2010 predict adoption to reach 45 million users. According to Business Week, from the last six months of 2004 to the first six months of 2005, the number of podcasts published multiplied by 2500 percent.

Podcasting is the audio version of an RSS newsfeed. You may have noticed the RSS or Atom icon on your favorite news site. With the help of an application called an aggregator, a user can subscribe to a newsfeeds, which will automatically download the newest stories directly to the local desktop for later reading. RSS is the popular XML format that holds the subscription information.

A podcast generally uses an RSS file nearly identical to a newsfeed to allow podcast aggregators (or pod- catchers) to subscribe to an audio feed. Audio files are downloaded by the aggregator (often MP3 or AAC format) into a computer or media device. You can use a computer (or more often, an MP3 player or iPod) to listen to the content. The most popular single podcasting site is Apple’s iTunes Web site.

Community Builder (CB) is an open source extension to Joomla that provides extensive broadening of Joomla’s user management features. It is one of the most popular extensions in the Joomla world. The capabilities of CB include the following:

❑       Managed passwords and groups

❑       Avatar image for users