Runtime evaluation of ontology-based reconfiguration of distributed embedded real-time systems

In modern safety-relevant applications a high degree of dependability and fault tolerance is demanded, which is obtained by the application of fault-tolerance techniques. Most of those techniques build on the active replication of sensors, actuators and computational components. During system design, explicit redundancy involves a fundamental trade-off between the number and types of tolerated faults and the resulting cost of increased reliability. Usually in such systems also implicit redundancy exists which is given by the vast number of measuring and actuation devices used to monitor, predict and control the physical process. Most common fault-tolerance techniques are designed to tolerate faults considered in the fault hypothesis of a system. However, they are not capable to benefit from implicit redundancy or to mitigate unforeseen failures. An effective technique to counteract these problems is ontology-based dynamic reconfiguration, which exploits implicit redundancy in the system to recover from failures. In order for dynamic reconfiguration to be applicable for embedded real-time systems, a temporal bound for system recovery has to be guaranteed. In this paper an approach for ontology-based reconfiguration is presented which can be performed within bounded time. The theoretical runtime considerations regarding the proposed technique are underlined by the results of reconfiguration experiments.