Real Time/Reactive Operation
- Real time: correctness of result is a function of time it is
       delivered
  - Not necessarily "real fast" -- consistency may be more
       important than raw speed
  - Worst case performance often limits design
- Reactive: computation rate is in response to external events
  - Periodic events can be scheduled statically
  - Aperiodic events must be statistically predicted, and (to
       avoid overdesign) dynamically scheduled when possible
Design challenges:
  - Least pessimism in worst case analysis
  - Accurate performance prediction before system is built