Statistical dependencies

In a database where numeric data has been obtained by inaccurate methods (measurements, calculations involving error propagation) it is unlikely to have equal stored values for a single, repeatedly measured/calculated value. As a result, instances which should satisfy but actually “nearly” satisfy a functional dependency cannot be decomposed. For such cases, we introduce the notion of statistical dependency (sd) as an extension of functional dependencies (fds). We show how the well-known axioms for fds can be used in the case of sds; decompositions w.r.t. sds are also presented. The resulting decomposition can be used to answer statistical queries. Finally, we study a possible way of generalizing the multivalued dependencies in the same manner