Wow, Luis, your comment should be a post, somewhere!!

Information Architecture: how it’s structured
Interaction Design: how it behaves
Information Design/Visual Design: how it looks

Front end
XHTML – How is structured
JS – How it behaves
CSS – How it looks

Backend
Model – Data and structure
Controller – Behaviour
View – the look, the skin of the system

Restaurant (I don’t know if I’m kidding here…)
Kitchen: data, ingredients, structure…
Waiter: behaviour, orders
Table: presentation, look

From my humble point of view, all of these layers in any of the domains (conceptual, logical, physical) has a lot to do with design. Maybe I live in a special place sorrounded by programmers and developers who act_as_designers ;-)

As a pattern, we’ve got three layers: a fundation, an intermediary which routes actions betwwen surface and fundation and a surface, the part that the user thinks is the system (because, from the user’s perspective, behind the surface there’s magic).

I’m not a philosopher, maybe I’m saying stupid things.