Effective timestamping in databases |
| |
Authors: | Kristian Torp Christian S Jensen Richard T Snodgrass |
| |
Affiliation: | Department of Computer Science, Aalborg University, Fredrik Bajers Vej 7E, DK-9220 Aalborg ?st, Denmark; e-mail: {torp,csj}@cs.auc.dk, DK Department of Computer Science, University of Arizona, Tucson, AZ 85721, USA; e-mail: rts@cs.arizona.edu, US
|
| |
Abstract: | Many existing database applications place various timestamps on their data, rendering temporal values such as dates and times
prevalent in database tables. During the past two decades, several dozen temporal data models have appeared, all with timestamps
being integral components. The models have used timestamps for encoding two specific temporal aspects of database facts, namely
transaction time, when the facts are current in the database, and valid time, when the facts are true in the modeled reality.
However, with few exceptions, the assignment of timestamp values has been considered only in the context of individual modification
statements.
This paper takes the next logical step: It considers the use of timestamping for capturing transaction and valid time in the
context of transactions. The paper initially identifies and analyzes several problems with straightforward timestamping, then
proceeds to propose a variety of techniques aimed at solving these problems. Timestamping the results of a transaction with
the commit time of the transaction is a promising approach. The paper studies how this timestamping may be done using a spectrum
of techniques. While many database facts are valid until now, the current time, this value is absent from the existing temporal types. Techniques that address this problem using different
substitute values are presented. Using a stratum architecture, the performance of the different proposed techniques are studied.
Although querying and modifying time-varying data is accompanied by a number of subtle problems, we present a comprehensive
approach that provides application programmers with simple, consistent, and efficient support for modifying bitemporal databases
in the context of user transactions.
Received: March 11, 1998 / Accepted July 27, 1999 |
| |
Keywords: | :Transactions – Timestamping – NOW– Valid time – Transaction time |
本文献已被 SpringerLink 等数据库收录! |
|