Viable diagnosis of complex active systems

An active system (AS) is a network of communicating automata. A complex active system (CAS) is a hierarchy of communicating active systems. By inspiration of biological systems, organized in a hierarchy of subsystems, the interaction between automata in an AS gives rise to an emergent behavior at a superior AS, which is unpredictable from a knowledge of the behavior of the communicating automata only. Real systems can be conveniently modeled as CAS's, in order to be monitored and diagnosed by automated techniques. A diagnosis method for CAS's is presented, with viability being a major requirement: despite the complexity of the system, diagnosis shall be performed efficiently. This is supported by lazy techniques, which allow for the sound and complete solution of the diagnosis problem.