You are responsible for writing the specification for a software system that controls a network of EPOS (electronic point of sale) terminals in a store. The system accepts bar code information from a terminal, queries a product database and returns the item name and its price to the terminal for display. The system must be continually available during the store’s opening hours.

Giving reasons for your choice, choose appropriate metrics for specifying the reliability of such a system and write a plausible reliability specification that takes into account the fact that some faults are more serious than others.

Suggest four functional requirements that might be generated for this store system to help improve system reliability.