Walter,

>I'm sure you know this, but for the lurkers: There is a difference between the definition of tiers and layers. One executable can consist out of many layers. Layers are logical separation of levels of implementation. Each layer communicates with an upper or lower level through a defined interface. Tiers on the other hand are simiular to layers, but they generally run in different processes and even on other machines.

Could you please explain more the next:

>Exchanging a tier is easy, exchanging a layer within a might requires a recompile.

Thanks,

AT