Problem 3
Explain why inheritance is a potentially error-prone construct and why its use should be minimised when developing critical systems in an object-oriented language.
Problem 4
Discuss the problems of developing and maintaining ‘nonstop’ systems such as telephone exchange software. How might exceptions be used in the development of such systems?
Problem 5
Explain why you should explicitly handle all exceptions in a fault-tolerant system.
Problem 6
Briefly describe forward and backward fault recovery strategies. Why is backward fault recovery used more often than forward error recovery? Give two examples of classes of systems where backward error recovery might be used.
Problem 8
Design an abstract data type or object class called RobustList that implements forward error recovery in a linked list. You should include operations to check the list for corruption and to re-build the list if corruption has occurred. Assume that you can check corruption by maintaining forward and backward references to and from adjacent members of the list.
Problem 9
Suggest circumstances where it is appropriate to use a fault-tolerant architecture when implementing a software-based control system and explain why this approach is required.
Problem 10
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 you think this is a good suggestion.
Problem 11
Give two reasons why all the system versions in an N-version system may fail in a similar way.
