Wide Area Languages
Luca Cardelli
Microsoft Research
AppSem Brainstorming
slide 1

WAN Observable Phenomena
Physical Locations
- Observable because of the speed of light limit
- Preclude instantaneous actions
- Require mobile code
Virtual Locations
- Observable because of administrative domains
- Preclude unfettered actions
- Require security model and disconnected operation
Variable Connectivity
- Observable because of free-will actions, physical mobility
- Precludes purely static networks
- Requires bandwidth adaptability
Failures
- Unobservable because of asynchrony, domain walls
- Preclude reliance on others
- Require blocking behavior, transaction model
slide 2

Wide Area Languages
Languages for Wide Area Networks:
WAN-sound
- No action-at-a-distance assumption
- No continued connectivity assumption
- No security bypasses
WAN-complete
- Able to emulate surfer/roamer behavior

slide 3

Some steps towards Wide Area Languages:
- Ambient Calculus (with Andy Gordon)
- Service Combinators (with Rowan Davies)
slide 4