A logic for handling time in temporal databases

An approach to the handling of time in query languages of historical database management systems is outlined. The approach is based on extending Boolean and comparison operators by allowing their operands to be sets of time intervals. The proposed temporal logic is shown to satisfy the properties of the normal Boolean logic. A relational-calculus query language using the extended logic is proposed. A new syntax for retrieval statements is defined in order to separate the process of selecting entities (tuples) and the process of selecting required values of temporal attributes from the chosen entities. The extension presented in this paper offer a good degree of flexibility in expressing different temporal requirements