Software Reliability Estimation under Uncertainty: Generalization of the Method of Moments

Traditionally, reliability models of component-based software systems compute the point estimate of system reli-ability by plugging point estimates of unknown parameters into the model. These models discard the uncertainty of the parameters, that is, do not attempt to answer the question how parameters uncertainties affect the estimates of system reliability. In this paper we focus on uncertainty analysis in software reliability based on method of moments. In par-ticular, we present a generalization of our earlier work that allows us to consider the uncertainty in the operational pro-file (i.e., the way software is used) in addition to the uncer-tainty in components failure behavior (i.e., component re-liabilities) considered earlier. The method of moments is an approximate analytical method that allows us to gener-ate system reliability moments based on (1) the knowledge of software architecture reflected in the expression of sys-tem reliability as a function of component reliabilities and frequencies of control transfer between components, (2) es-timates of the moments of components reliabilities, and (3) estimates of the moments of probabilities of control transfer between components. Further, we apply the method of mo-ments on two case studies and discuss its advantages and disadvantages.