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.

What will be an ideal response?

Advantages of N-version programming
1. Increases design diversity so probability of faults that result in failures
should be reduced
2. Increases availability of the system
Disadvantages
1. Increased cost because of the need to use independent development teams
2. Increased software complexity because of the need for a fault tolerant
controller. Increased complexity increases the probability of error
3. Improvement in reliability in practice is limited because of the possibility of
common errors made by different development teams.
4. Operator error, where the wrong dose is set is the most likely error for this
type of system. N-version programming does not help with this.
N-version programming would not be a good design strategy for this type of
software. There is no need for high availability and the increased complexity and
cost would make the overall cost of the machine too high.