codeigniter as compared to Joomla framework

[eluser]elmne[/eluser]
I have a question. Codeigniter is a framework, and Joomla is also a framework on which teh CMS is built.


JOOMLA

Joomla has the following

Template
- with position tags

URL
- Urls are based on menus
The template is attached to a menu or is specified as default
- Modules show up wherever the position is on a template (unless resticted by menu in module settings)
- Component displays component's content based on level within the structure (homepage, section, category, item)
- Navigation to structure level is aided by the menu

Controller
- Modules, Components have controlle rthat validates data, receives input, calls model objects, passes output to specified tags in code

Model
- Modules, Components have models that contains functions which process the data and perform given tasks



CODEIGNITER

For codeigniter, there is similarity with the model and controller.


The difference seems to be that with Codeigniter, URLs are determined by Controlllers.

My question would be, how does one create what are like modules in Codeigniter so that data is displayed in a given page position and can be configured?

At the moment, the Controller not only determines teh URL, but also the tags that correspond to the Viewer to which data will be passed.


Is there a way to have
- a template that defines positions.
- Then each controller working as a module (as a module can have one or more functions) and being assigned to be displayed on a template in a given position
- The viewer for the module is the one that loads up for a given position
- And then one controller that manages URLs, such as the menu controller


Or how can a similar functionality be achieved?