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Real-Time Databases

Real-Time Databases,10.1007/BF01264051,Distributed and Parallel Databases,Krithi Ramamritham

Real-Time Databases   (Citations: 387)
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Data in real-time databases has to be logically consistent as well as temporally consistent. The latter arises from the need to preserve the temporal validity of data items that reflect the state of the environment that is being controlled by the system. Some of the timing constraints on the transactions that process real-time data come from this need. These constraints, in turn, necessitate time-cognizant transaction processing so that transactions can be processed to meet their deadlines. This paper explores the issues in real-time database systems and presents an overview of the state of the art. After introducing the characteristics of data and transactions in real-time databases, we discuss issues that relate to the processing of time-constrained transactions. Specifically, we examine different approaches to resolving contention over data and processing resources. We also explore the problems of recovery, managing I/O, and handling overloads. Real-time databases have the potential...
Journal: Distributed and Parallel Databases - DPD , vol. 1, no. 2, pp. 199-226, 1993
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    • ...priority assignment strategy has its adaptive characteristics, the distribution of a fixed priority scheduling strategy is not for real-time Affairs as provide a reliable guarantee of, and the use of priority scheduling methods can not accurately specify the timing of transaction execution [7]...

    Shiyang Liuet al. Research based on database transactions

    • ...There are two correctness constraints (or temporal consistency constraints) on realtime data, namely the absolute consistency and the relative consistency [1],[2]...

    Tian Baiet al. Scheduling queries with relative consistency constraints

    • ...One efficient way to determine the correctness of real-time data in a RTDBS is to define a validity constraint (Song and Liu 1995; Ramamritham 1993; Kuo and Mok 1992, 1993 ;H o et al.1997; Gerber et al. 1994; Xiong et al. 2002, 2005; Kang et al. 2002; Lam et al. 2004; Gustafsson and Hansson 2004a, 2004b; Chen and Mok 2004; Xiong and Ramamritham 2004 )o rage constraint (Burns and Davis 1996), which determines a validity interval length for ...
    • ...One of the proposed approaches is the Half-Half (HH) scheme (Ramamritham 1993 ;H o et al.1997) in which an update transaction has a fixed period that is half of the validity interval...
    • ...Definition 2.1 A real-time data object (Xi ) at time t is temporally valid (or absolutely consistent) if, for its j th update finished latest before t, the sampling time (ri,j )p lus thevalidity interval (Vi ) of the data object is not less than t, i.e., ri,j + Vi ≥ t (Ramamritham 1993)...
    • ...The actual length of the temporal validity interval of a real-time data object is application dependent (Ramamritham 1993, 1996; Locke 1997)...

    Ming Xionget al. DESH: overhead reduction algorithms for deferrable scheduling

    • ...Temporal consistency can be measured in two ways: absolute consistency and relative consistency [21]...
    • ...Transactions in a real-time database environment are subdivided into two classes: update transactions and user transactions [21]...
    • ...A real-time database is a database in which both the data and the operations upon the data may have timing constraints [21]...
    • ...The mostly used data model for real-time databases was the relational model [21]...
    • ...A non real-time data is a classical data found in conventional databases, whereas a real-time data has a validity interval beyond which it becomes useless [21]...
    • ...Our real-time data model is based on the model introduced in [21] and we associate to this model the notion of maximum data error (MDE) introduced in [1]...
    • ...TS (TimeStamp) is used to store the last time at which the attribute’s value was updated [21]...
    • ...VD (Validity Duration) is used to store the lenght of absolute validity interval (denoted by avi) of the attribute value [21]...
    • ...A data item is considered absolutely consistent (fresh) with respect to time as long as the age of the data value is within a given interval [21]...
    • ...A periodic method must complete its execution before the deadline, otherwise the value to be written will be considered obsolete [21]...

    Nizar Idoudiet al. A framework to model real-time databases

    • ...Systems suitable to the management of these kinds of data with QoS guarantees are real-time database systems (RTDBSs) [15] [16]...

    Bechir Alayaet al. Feedback architecture for multimedia systems

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