A suitable relational model for temporal databases (abstract only)

Abstract

The relational approach has been applied very literally to temporal databases. For example, the SALARY and DEPT of an employee do not necessarily change at the same time, resulting in a split of information into two tables: NAME SALARY START END and NAME DEPT START END, where START and END are instants of time, treated as special attributes. A unit of information, such as salary of an employee, is further split into several tuples. Normal forms, dependencies and other nice concepts of relational databases remain inapplicable to the temporal case. We propose that a tuple, the fundamental molecular unit of information, be viewed as a function from a union of finitely many intervals of time into domains of attributes. This eliminates the problems stated above. It gives rise to elegant relational algebra, tuple calculus and other query languages and brings temporal databases within the classical framework. It is hoped that this model will draw the attention of researchers to temporal databases.