Research issues in real-time database systems

Cataloged from PDF version of article.Today's real-time systems are characterized by managing large volumes of data. Efficient database management algorithms for accessing and manipulating data are required to satisfy timing constraints of supported applications. Real-time database systems involve a new research area investigating possible ways of applying database systems technology to real-time systems. Management of real-time information through a database system requires the integration of concepts from both real-time systems and database systems. Some new criteria need to be developed to involve timing constraints of real-time applications in many database systems design issues, such as transaction/query processing, data buffering, CPU, and IO scheduling. In this paper, a basic understanding of the issues in real-time database systems is provided and the research efforts in this area are introduced. Different approaches to various problems of real-time database systems are briefly described, and possible future research directions are discussed

Maintaining temporal consistency of discrete objects in soft real-time database systems

A real-time database system contains base data items which record and model a physical, real-world environment. For better decision support, base data items are summarized and correlated to derive views. These base data and views are accessed by application transactions to generate the ultimate actions taken by the system. As the environment changes, updates are applied to base data, which subsequently trigger view recomputations. There are thus three types of activities: Base data update, view recomputation, and transaction execution. In a real-time database system, two timing constraints need to be enforced. We require that transactions meet their deadlines (transaction timeliness) and read fresh data (data timeliness). In this paper, we define the concept of absolute and relative temporal consistency from the perspective of transactions for discrete data objects. We address the important issue of transaction scheduling among the three types of activities such that the two timing requirements can be met. We also discuss how a real-time database system should be designed to enforce different levels of temporal consistency.published_or_final_versio

Pricing of Information Services Using Real-Time Databases: A Framework for Integrating User Preferences and Real-Time Workload (Best Paper Runner Up)

Many revolutionary information products are being offered or envisioned in electronic commerce setting. Since an economic paradigm and mass customization are implicit in electronic commerce, these products must be produced and delivered at appropriate prices with user desired service characteristics such as response time, correctness, and completeness. In this research, we investigate the information services pricing with response time (or delay) as the only service characteristic since response time can implicitly characterize other quality attributes such as correctness. In order to recognize customers’ preferences, real-time databases, where transaction processing is time-cognizant, are central to information providers and can be thought of as “manufacturers” of customized products. We propose to capture user preferences by a priority pricing mechanism based on economic theory. This pricing is concerned with database access and is independent of content pricing. Our approach has a natural overload1 management and admission control2 techniques that can potentially increase collective benefits. Our model is evaluated using simulation and is shown to outperform a system without access pricing mechanism with respect to both system wide benefits and RTDB performance

Collective Value QoS: A Performance Measure Framework for Distributed Heterogeneous Networks

When users' tasks in a distributed heterogeneous computing environment are allocated resources, and the total demand placed on system resources by the tasks, for a given interval of time, exceeds the resources available, some tasks will receive degraded service, receive no service at all, or may be dropped from the system. One part of a measure to quantify the success of a resource management system (RMS) in such an environment is the collective value of the tasks completed during an interval of time, as perceived by the user, the application, or the policy maker. For the case where a task may be a data communication request, the collective value of data communication requests that are satisfied during an interval of time is measured. The Flexible Integrated System Capability (FISC) measure defined here is one way of obtaining a multi-dimensional measure for quantifying this collective value. While the FISC measure itself is not sufficient for scheduling purposes, it can be a critical part of a scheduler or a scheduling heuristic. The primary contribution of this work is providing a way to measure the collective value accrued by an RMS using a broad range of attributes and to construct a flexible framework that can be extended for particular problem domains.DARPA/ITO Quorum ProgramDARPA/ISO BADD ProgramOffice of Naval Research under ONR grant number N00014-97-1-0804DARPA/ITO AICE program under contract numbers DABT63-99-C-0010 and DABT63-99-C-0012DARPA/ITO Quorum ProgramDARPA/ISO BADD ProgramOffice of Naval Research under ONR grant number N00014-97-1-0804DARPA/ITO AICE program under contract numbers DABT63-99-C-0010 and DABT63-99-C-0012Approved for public release; distribution is unlimited

A Resource-Based Analysis of Outsourcing: Evidence from Case Studies

The central role that information technology plays in the management of companies, the massive investments that are required, and a preoccupation for rationalization explain in good part the renewed interest in the strategies used for information systems sourcing. In-house provision is often seen as the best way to provide an organization with IT services that are well adapted to support its business activities while preserving its trademark processes and know-how. On the other hand, critics argue that a better solution is to outsource those IT activities to specialists, thus permitting the company to focus on its core business. The choice of a sourcing mode has an impact on the ability of the firm to implement its systems and ultimately to compete in its field of business. In order to better understand under what conditions a firm should choose one sourcing mode over another, we argue that it is necessary to analyze the interactions between a firm's competencies and the strategic value of those competencies. This is investigated using evidence from 21 information system projects. The0501n findings were that the best predictor of success and failure, by far, is the fit between the governance mode and the position of the project in the value/availability matrix. Another interesting finding is that no sourcing mode per se seems to lead to successful outcomes. It is always a matter of selecting the appropriate mode for each situation. De plus en plus, les technologies de l'information sont au centre des préoccupations des gestionnaires. Elles commandent des investissements massifs et peuvent être gérées de diverses manières. Traditionnellement, une gestion interne était favorisée pour fournir à l'organisation des services sur mesure et pour protéger des pratiques uniques, permettant à l'organisation de se différencier. Les détracteurs de cette approche soutiennent que l'impartition est un meilleur choix. L'impartition permet à la firme de se concentrer sur ses compétences de bases tout en lui donnant accès à des spécialistes de pointe. Pour mieux comprendre le lien entre les compétences de la firme et l'impartition, 21 projets sont étudiés. Les résultats indiquent que le meilleur prédicteur de succès est l'adéquation entre le mode de gestion et le profil de compétences de la firme.Outsourcing of IT, resource-based theory, IT resources, Impartition, approche centrée sur les resources, étude de cas

An Evaluation of Network Access Protocols for Distributed Real-time Database Systems

Cataloged from PDF version of article.The results of a considerable number of works addressing various features of real-time database systems (RTDBSs) have recently appeared in the literature. An issue that has not received much attention yet is the performance of the communication network configuration in a distributed RTDBS. In this article, we examine the impact of underlying network architecture on the performance of a distributed RTDBS. In particular, we evaluate the real-time performance of distributed transactions in terms of the fraction of satisfied deadlines under various network access strategies. We also critically examine the common assumption of constant network delay for each communication message exchanged in a distributed RTDBS. (C) 1997 by Elsevier Science Inc