What Happened ? " vs \ What is Ab ? " { A Theoretical Framework

This paper presents a new view of model-based diagnosis for evolu-tive systems. The possible behaviors of the evolutive system are captured by a set of events that can aaect its current state. Diagnosing amounts to determining the history of the system, in terms of a sequence of events representing what may have happened to the system between two or more successive observations. This approach is particularly useful when explaining successive observations requires taking the history of the system into account. It allows precedence constraints between faults, as well as intermittent and non-intermittent faults to be modeled. It provides a uniied representation and treatment of the various types of evolutions of the system's state: evolutions due to internal faults, to exogeneous events, as well as to repair actions.