Towards Causal Explanations of Property Violations in Discrete Event Systems

Model-Based Diagnosis of discrete event systems (DES) usually aims at detecting failures and isolating faulty event occurrences based on a behavioural model of the system and an observable execution log. The strength of a diagnostic process is to determine what happened that is consistent with the observations. In order to go a step further and explain why the observed outcome occurred, we borrow techniques from causal analysis. As opposed to the classical fault diagnosis problem, we consider that a system is failing as soon as a specific behavioural property is violated by the current run of the system. We then formally define different notions of explanation for DES in order to extract the relevant part of a property violation that can be understood by a human operator.