<i>Recently, attention has been focussed on</i> historical databases <i>(HDBs), representing an enterprise over time. We have developed a new language,</i> TQuel, <i>to query an HDB. TQuel is a superset of Quel, the query language in the Ingres relational database management system. This paper provides an overview of the language, motivating the various… (More)
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)
Database needs are changing, driven by the Internet and increasing amounts of scientific and sensor data. In this article, the authors propose research into several important new directions for database management systems.
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)
Aggregate computation, such as selecting the minimum attribute value of a relation, is expensive, especially in a temporal database. We describe the basic techniques behind computing aggregates in conventional databases and show that these techniques are not efficient when applied to temporal databases. We examine the problem of computing constant intervals… (More)