Zend is a PHP class Library
Symfony and Ruby on Rails are Web Application Frameworks extendible by the Developers.
Joomla! CMS version 1.5 or later is a Content Management Framework (CMF) which is extendible by both the Developers and the Users.
You noticed the evolution pattern?
now go through this presentation!
[tags]cms, content management, framework, joomla, johanjanssens [/tags]