The 1.5 and 1.6 versions of the Joomla! CMS are based on a three-tiered system that consists of the following:
- The top, Extensions layer, consists of Extensions to the Joomla Framework and its applications:
- The middle, Application layer, consists of applications that extend the Framework JApplication class. Currently, there are four applications included in the Joomla distribution:
- JInstallation is responsible for installing Joomla on a web server and is deleted after the installation procedure has been completed.
- JAdministrator is responsible for the back-end website administration.
- JSite is responsible for the front-end of the website.
- XML-RPC supports remote administration of the Joomla website.
- The bottom, Framework layer, consists of: