Analyzing the Behavior of Embedded Systems Concerning Gracefull Degradation

Reliability is a crucial aspect of embedded systems. Achieving reliable systems is based on fault-tolerance covering hardware failures and an adequate design process that minimizes development faults. e.g., model checking may be used to verify small and medium sized systems. However, we are interested in designing large distributed embedded systems with weak safety requirements like building automation systems or automotive comfort systems. Such systems confront hardware failures by graceful degradation instead of using redundant stand-by systems. Nevertheless, during system development we also need to analyze the failure behavior of our systems to achieve predictable gradations of their functionality. Today, the analysis will usually be done by standard methods like FTA and FMEA considering the existence of faults, only. Gradations of errors, as we are interested in, are not regarded. We therefore developed an advanced failure behavior analysis method which yields more sophisticated and graded results. We obtain comprehensive results by assigning a quality description to all the information in a system and extending the pure information flow to an information quality flow, that models system failure behavior, too. This article gives a detailed overview of that analysis method.