Software Fault Tolerance

This chapter presents a non-homogeneous Poisson progress reliability model for N-version programming systems. We separate all faults within NVP systems into independent faults and common faults, and model each type of failure as NHPP. We further develop a reliability model for common failures in NVP systems and also present a model for concurrent independent failures in NVP systems. By combining the CF model and the CIF model together, we establish an NHPP reliability model for NVP systems. We also give an example to illustrate how to estimate all unknown parameters by using the maximum likelihood estimation method, and how to compute the variances for all parameter estimates in order to obtain the confidence intervals of NVP system reliability prediction.