TEMPORAL DATABASES WITH 2-DIMENSIONAL TIME - MODELING AND IMPLEMENTATION OF MULTIHISTORY

In this paper, we present an interpretation of the temporal database w ith two-dimensional time (also termed bitemporal databases in the lite rature) and propose an implementation. We define the notions of two-di mensional temporal validity and valid pattern. Using valid patterns, t he notion of multihistory, which is a collection of a data object's hi story at every viewpoint, is developed. We show how a multihistory can be modeled using the relations. We define data manipulation operation s over multihistory. Algorithms for implementing a multihistory are co uched in the relational data model using the temporal data manipulatio n operations. Finally, set operations over multihistory are illustrate d.