[smitty1e]

I think it needs three areas, not two:

1. User space

2. Kernel

3. Hardware/network

The kernel protects users from hardware, and hardware from users.

[topspin]

This is reasonable and correct. I would also have found places in that map for: dcache, block devices, character devices, scheduler, page cache and console/tty/pty. The first two replace "filesystem hierarchy". The second and third are ancient and fundamental classes of UNIX devices.

[t1tos]

this is analagous to the fs hierarchy: root protects from the user