HW4 Chapters 11 & 12

11.4 What is the common characteristic of all architectural styles that are geared to supporting software fault tolerance?

Redundant and diverse hardware and software are shared characteristics of different architectural styles.

11.7 It has been suggested that the control software for a radiation therapy machine, used to treat patients with cancer, should be implemented using N-version programming. Comment on whether or not you think this is a good suggestion.

This is a good idea because something as serious as radiation therapy should have multiple checks in place in order to help prevent any errors in the system.

11.9 Explain why you should explicitly handle all exceptions in a system that is intended to have a high level of availability

All exceptions should be handled in a system since if any exception is left unchecked it can high a high probability of breaking the system, and thus prolonging deadlines, loss of data, and loss profit, etc. could occur.

12.5 A train protection system automatically applies the brakes of a train if the speed limit for a segment of track is exceeded, or if the train enters a track segment that is currently signaled with a red light (i.e. the segment should not be entered). There are two critical safety requirements for this train protection system:

• The train cannot go faster than the speed limit.
• The train cannot proceed on a track with a red light.