An Overview of Real-Time Database Systems

Abstract

AN OVER VIEW OF REAL-TIME DA T ABASE SYSTEMS Ben Kao 1;2 and Hector Garcia-Molina 2 1 Princeton University, Princeton NJ 08544, USA 2 Stanford University, Stanford CA 94305, USA 1 Introduction Traditionally, real-time systems manage their data (e.g. chamber temperature, aircraft locations) in application dependent structures. As real-time systems evolve, their applications become more complex and require access to more data. It thus becomes necessary to manage the data in a systematic and organized fashion. Database management systems provide tools for such organization, so in recent years there has been interest in "merging" database and real-time technology. The resulting integrated system, which provides database operations with real-time constraints is generally called a real-time database system (RTDBS) [1]. Like a conventional database system, a RTDBS functions as a repository of data, provides effcient storage, and performs retrieval and manipulation of information. However, as a part of a real-time system, whose "tasks" are associated with time constraints, a RTDBS, has the added burden of ensuring some degree of confidence in meeting the system's timing requirements. Example applications that handle large amounts of data and have stringent timing requirements include telephone switching (e.g. translating an 800 number into an actual numbradar tracking and others. Arbitrage trading, for example, involves trading commodities in different markets at different prices. Since price discrepancies are usually short-lived, automated searching and processing of large amounts of trading information are very desirable. In order to capitalize on the opportunities, buy-sell decisions have to be made promptly, often with a time constraint so that the financial overhead in performing the trade actions are well compensated by the benefit resulting from the trade. As another example, a radar surveillance system detects aircraft "images" or "radar signatures". These images ar