4
Modular Imperfect Coverage
A hierarchical system (HS) is a system whose underlying architecture can be characterized by multiple layers, with each layer housing different modules and/or components. In an HS, the failure behavior of an upper level often relies on the failure behavior of its lower level(s) [1,2].
Chapter 3 focuses on the traditional kill‐all imperfect fault coverage, where an uncovered component fault can lead to the failure of the entire system even when adequate redundancies still remain [3,4]. In an HS, however, the hierarchical nature of the system may aid in the fault coverage [ 2 ,5]: if an undetected fault escapes from one level of the system, it may be tolerated at a higher level. In other words, the extent of the damage from an uncovered component fault in a certain layer of a system does not necessarily cause the entire system loss. On the other hand, a fault can cause the entire system to fail only if it remains uncovered through all levels of the system...