Adjudicators for diverse-redundant software: problem statement

The adjudication problem arises when fault-lolerant components are realized using replication. It consists in the definition of a mechanism for the choice of a correct value as the output value for the redundant component, starting from the individual results produced by the replicas of which the redundant component is composed. The purpose of this report is to investigate the use of probabilistic knowledge about errors/faults among the components of the system to obtain good adjudication functions. First, a terminology for the specification of robust redundant components is introduced. Then, an optimal adjudication function is defined, which has the highest probability of producing correct results, given the information available to it. Last, a method for the evaluation or different adjudication functions, useful for the choice of the best adjudication function for a real application, is outlined.