A new measure of temporal consistency for derived objects in real-time database systems

A real-time database system (RTDBS) must satisfy the timing constraints of its transactions as well as the temporal consistency constraints of its temporal data. The data is considered to be temporally consistent if it is absolutely and relatively consistent. A data object is absolutely consistent if its age is younger than an absolute threshold, and a set of data objects is considered to be relatively consistent if the dispersion of ages is smaller than a relative threshold. It is often difficult to select appropriate values for the thresholds that satisfy both absolute and relative consistency, especially in the case of objects whose values are derived (derived objects). In this paper we propose a new measure of temporal consistency for derived objects that is based on a new definition for the age of the derived object. Our proposed age provides additional insight into the temporal consistency of derived data objects and is useful for real-time database design and management.