Here excerpted from SCEA Beta Objectives: 1.2 Describe how the principle of "separation of concerns" has been applied to the main system tiers of a Java EE application. Tiers include client (both GUI and web), web (web container), business (EJB container), integration, and resource tiers. 1.3 Describe how the principle of "separation of concerns" has been applied to the layers of a Java EE application. Layers include application, virtual platform (component APIs), application infrastructure (containers), enterprise services (operating system and virtualization), compute and storage, and the networking infrastructure layers.
I've got a general idea that layers represents the logical view of the application while tier represents physical view of the application. What confused me is that I just can't find any corresponding concepts in the above lists according to this understanding. I mean for example, shouldn't presentation be a LAYER?
Did I misunderstand the ideas? Any official resource addressing this issue from SUN? Also better to know from those pioneers of SCEA BETA if this is a big deal to the exam?