Shared Models in Different Modules

Hi List,

I asked a question about Shared View Scripts some days ago
and you recommend me to use Zend_Layout. I have a similiar
question about Models in a modular-dir-structure.

A website always has a homepage, which usually consists
of links to other sections (modules). Thus, the default modules
should have access to other modules' models.

Isn't this an architectural disease? It sounds that these shared
models are destroying the Modular-based building.

How can I have access to different models in different modules.
It is critical for default module (homepage) to have access to
whole website's content.

What is the best place to put centralized code (including
bootstraper, shared views, shared models?)