Top down


Apps:
- regular apps (web server, web browser, etc.)

Shell:
- shell

Interaction and I/O:
- storage management
- network stack
- terminal

Resource Management and Protection:
- resource management and accounting
- principals
- power management

Devices:
- device drivers 
- bus management
- device management

Synchronisation:
- lock service

Communication and Process Management:
- binding
- naming
- group communication
- routing
- process management
- threading

skb:
- skb

Base functionality:
- capability management
- memory allocation
- basic communication
- virtual memory??