Fault tree models for the analysis of complex computer-based systems

In this paper we present a synthesis of several techniques into a single methodology that can solve both dynamic and static fault trees, and which is applicable to the analysis of hardware, software and humanware in complex computer-based systems. The methodology combines those techniques into a unified fault tree methodology which we call SHADE Tree. SHADE Tree provides a high-level decomposition of the system fault tree model into the static and dynamic fault trees. Static fault trees, which contain only traditional fault tree gates (i.e. AND, OR, R-of-N, etc.) are solved using the binary decision diagram approach. Dynamic fault trees, which contain at least one special dynamic gate as well as traditional fault tree gates, are solved using Markov methods.