An authorization system for temporal data

We present a system, called the Temporal Data Authorization Model (TDAM), for managing authorizations for temporal data. TDAM is capable of expressing access control policies based on the temporal characteristics of data. TDAM extends existing authorization models to allow the specifications of temporal constraints on data, based on data validity, data capture time, and replication time, using either absolute or relative time references. The ability to specify access control based on such temporal aspects were not supported before. The formulae are evaluated with respect to various temporal assignments to ensure the correctness of access control.