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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)
While " now " is expressed in SQL as CURRENT_TIMESTAMP within queries, this value cannot be stored in the database. However, this notion of an ever-increasing current-time value has been reflected in some temporal data models by inclusion of database-resident variables, such as " now, " " until-changed, " " ∞, " " @ " and " –. " Time variables are very(More)