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On Earliest Deadline First Scheduling for Temporal Consistency Maintenance

01 November 2008

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The problem of maintaining temporal validity of data is motivated by the need for a real-time system to track its environment correctly. This is usually accomplished by the periodic execution of sensor transactions. But, the period and deadline assignmemt problem for periodic sensor transactions has not received the attention that it deserves. An exception is the More-Less scheme for maintaining temporal validity of real-time data [17,7]. It uses the Deadline Monotonic (DM) algorithm [10] for scheduling periodic sensor transactions and achieves better processor utilization than the traditionally used Half-Half method. A critical examination of the More-Less scheme however reveals that it is unable to deal with sensor transactions whose deadlines are greater than their periods. Motivated also by the desire to deal with dynamic priority based Real-Time systems, in this paper we examine the problem of temporal vailidity maintenance using the Earliest Deadline First (EDF) algorithm. Because the existing More-Less method cannot be easily extended to deal with EDF, we start from first principles and proceed in three steps.