Unification of temporal data models

A conceptual temporal data model that captures the time-dependent semantics of data while permitting multiple data models at the representation level is described. A conceptual notion of a bitemporal relation in which tuples are stamped with sets of two-dimensional chronons in transaction-time/valid-time space is defined. A tuple-timestamped first normal form representation is introduced to show how the conceptual bitemporal data model is related, by means of snapshot equivalence, with representational models. Querying within the two-level framework is discussed. An algebra is defined at the conceptual level and mapped to the sample representational model in such a way that new operators compute equivalent results for different representations of the same conceptual bitemporal relation