The actual link is here: http://www.magentocommerce.com/wiki/Designing-for-Magento/
Thank you for reading carefully the post. It should have been read as “blocks” not “models”.
The charts explaining the architecture of Magento will be posted as soon as we’ll get to it, but meanwhile here’s short overview:
To allow greater flexibility with backend implementations, we have splited these to Object Models and Resource Models. Object Models are responsible for abstract logic of the models and Resource Models are for engine specific logic.
Here we have Layouts, Blocks and Templates. Layouts are XML files defining Blocks tree structure and specifying Templates for them to use.
these are the Zend_Controller_Action compatible classes.
Let me know if you have more questions