Explain why it is practically impossible to validate reliability specifications when these are expressed in terms of a very small number of failures over the total lifetime of a system. Suggest...

Explain why it is practically impossible to validate reliability specifications when these are expressed in terms of a very small number of failures over the total lifetime of a system. Suggest appropriate reliability metrics for the classes of software system below. Give reasons for your choice of metric. Predict the usage of these systems and suggest appropriate values for the reliability metrics.                      ■ a system that monitors patients in a hospital intensive care unit                                                   ■ a word processor                                                                                                                                                               ■ an automated vending machine control system                                                                                                         ■ a system to control braking in a car                                                                                                                      ■ a system to control a refrigeration unit                                                                                                                       ■ a management report generator