Application of Systemability to Software Reliability Evaluation

This paper applies the concept of systemability, which is defined as the reliability characteristic subject to the uncertainty of the field operational environment, to the operational software reliability evaluation. We take the position that the software reliability characteristic in the testing phase is originally different from that in the user operation. First we introduce the environmental factor to consistently bridge the gap between the software failure-occurrence characteristics during the testing and the operation phases. Then we consider the randomness of the environmental factor, i.e., the environmental factor is treated as a random-distributed variable. We use the hazard rate-based model focusing on the software failure-occurrence time to describe the software reliability growth phenomena in the testing and the operation phases. We derive several operational software reliability assessment measures. Finally, we show several numerical illustrations to investigate the impacts of the consideration of systemability on the field software reliability evaluation.