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<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)
Outline • Temporal database • Real-time database Temporal Database • Time as an important domain • Valid time and transaction time – Valid time models events in reality – Trans. time models facts known by database • Temporal data, Temporal database – A database that supports some aspect of time. – He went to live on his own in Bigtown. Although he moved out… (More)
This paper provides a systematic and comprehensive study of the semantics of temporal databases. We rst examine how facts may be associated with time, speciically with one or more dimensions of valid time and transaction time. One common case is that of a bitemporal relation, in which facts are associated with exactly one valid time and one transaction… (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.
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)
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)
Although “<italic>now</italic>” is expressed in SQL and CURRENT_TIMESTAMP within queries, this value cannot be stored in the database. How ever, 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 “<italic>now</italic>”… (More)