Modeling redundancy: Quantitative and qualitative models

Redundancy is a system property that generally refers to duplication of state information or system function. While redundancy is usually investigated in the context of fault tolerance, one can argue that it is in fact an intrinsic feature of a system that can be analyzed on its own without reference to fault tolerance. Redundancy may arise by design, generally to support fault tolerance, or as a natural byproduct of design, and is usually unexploited. In this paper, we tentatively explore observable forms of redundancy, as well as mathematical models that capture them.