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A temporal database contains time-varying data. In a real-time database transactions have deadlines or timing constraints. In this paper we review the substantial research in these two previously separate areas. First we characterize the time domain; then we investigate temporal and real-time data models. We evaluate temporal and real-time query languages(More)
In <italic>valid-time indeterminacy</italic> it is known that an event stored in a database did in fact occur, but it is not known exactly <italic>when</italic>. In this paper we extend the SQL data model and query language to support valid-time indeterminacy. We represent the occurrence time of an event with a set of possible instants, delimiting when the(More)
This document 1 contains deenitions of a wide range of concepts speciic to and widely used within temporal databases. In addition to providing deenitions, the document also includes explanations of concepts as well as discussions of the adopted names. The consensus eort that lead to this glossary was initiated in Early 1992. The present glossary subsumes(More)
The relational algebra is a procedural query language for relational databases. In this paper we survey extensions of the relational algebra that can query databases recording time-varying data. Such an algebra is a critical part of a temporal DBMS. We identify 26 criteria that provide an objective basis for evaluating temporal algebras, Seven of the(More)