Reasoning about System-Degradation and Fault-Recovery with Deontic Logic

In this paper we outline the main characteristics of a deontic logic, which we claim is useful for the modeling of and reasoning about fault-tolerance and related concepts. Towards this goal, we describe a temporal extension of this formalism together with some of its properties. We use two different examples to show how some fault-tolerance concepts (like fault-recovery and system degradation) can be expressed using deontic constructs. The second example demonstrates how contrary-to-duty reasoning (when a secondary obligation arises from the violation of a primary obligation) is applied in fault-tolerant scenarios.