Handling sensed data in hostile environments

Abstract

Systems that track sensed data trigger alerts based on the evaluation of some condition. In the presence of loss data a conservative condition may not generate a necessary alert and an aggressive condition may generate an alert that could have never happened. We observe that some lost values can be predicted and suggest new classes of conditions that provide more accurate alerts. We motivate the use of such conditions, provide a method for comparing two condition systems, and investigate the systems' properties in both replicated and non replicated architectures. In addition, we propose a weak completeness property, discuss its merit and show a motivation for its use. Our main result shows that a triggering algorithm, used in one of our condition systems, strictly dominates another algorithm for conservative system, yet, both algorithms satisfy the same set of properties; thus, with some simple observations, we have a strong evidence for its optimality. © Springer-Verlag Berlin Heidelberg 2005.