START: System Testability Analysis and Research Tool

START, a software package for automatic test sequencing and testability analysis of complex, hierarchically described modular systems, is described, and its use in modeling systems is examined. START uses algorithms based on information theory, heuristic search, and graph theory to solve various faces of the test sequencing and testability analysis problems. A system is modeled in the failure space as a hierarchical directed graph with nodes denoting modules and testpoints and with AND nodes denoting redundancy. Interconnections among the nodes denote their immediate functional dependencies. START supports hierarchical testing in accordance with the maintenance strategy; a failure source may be isolated to a component or a module at any level. Other practical features include options to integrate diagnosis with repair (after partial diagnosis) in order to optimize test time, test cost, or test and repair cost. An interactive menu-mouse graphical interface serves as a high-level front end to these algorithms and enables the user to graphically enter and modify hierarchical functional models of systems. START presents the gist of the outputs of the testability analysis algorithms as a concise testability report consisting of important figures of merit