The TSQL2 Data Model

Abstract

Adding time to the relational model has been a daunting task [Bolour et al. 1982, McKenzie 1986, Soo 1991, Stam & Snodgrass 1988]. More than two dozen time-extended relational data models have been proposed over the last fifteen years [Snodgrass 1992]. Most of these are valid-time models. Each fact in a valid-time relation has associated the time when it is true in the modeled reality. Other models support transaction-time relations where each fact has associated the time when it is current in the database. A few support both valid and transaction time [Ben-Zvi 1982, Bhargava&Gadia 1989A, Snodgrass 1987, Snodgrass et al. 1993, Thompson 1991]; such models are termed bitemporal. As a whole, these data models are referred to as temporal data models [Jensen et al. 1994].