Software reliability allocation under an uncertain operational profile

The failure probability of a modular software system depends on the reliabilities of the modules and the software operational profile. The software operational profile estimated in the development phase has inherent uncertainty because estimation error is inevitable and the operational profile often changes in the operation phase. The software project manager must take this uncertainty into account, so that the customers will not suffer from an unacceptably large failure probability even when his/her operational profile deviates from the estimated one. In this paper, we formulate and solve three optimizing models for software reliability allocation under an uncertain operational profile. The numerical results indicate that when we take the uncertainty into account, the additional software development cost required is acceptably small.