Temporal Databases

Abstract

Apart from some primary keys and keys that rarely change, many attributes evolve and take new values over time. For example, in an employee relation, employees’ titles may change as they take on new responsibilities, as will their salaries as a result of promotion or increment. Traditionally, when data is updated, its old copy is discarded and the most recent version is captured. Conventional databases that have been designed to capture only the most recent data are known as snapshot databases. With the increasing awareness of the values of the history of data, maintenance of old versions of records becomes an important feature of database systems.