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Monitoring of timing constraints with confidence threshold requirements

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3 Author(s)
Chan-Gun Lee ; Dept. of Comput. Sci., Texas Univ., Austin, TX, USA ; Mok, A.K. ; Konana, P.

We propose an algorithm for monitoring timing constraints to satisfy confidence threshold requirements when there is uncertainty in the exact timing of event occurrences. In our model, a timed event trace is examined for possible satisfaction/violation with respect to a given set of timing constraints. Every event occurrence has a timestamp given by a time interval. Assuming that the time of occurrence is uniformly distributed over the time interval, our algorithm determines whether the probability that a timing constraint has been satisfied exceeds a specified threshold value. Timing constraints are composed of deadline and delay constraints for which satisfaction probabilities are defined. A confidence threshold is a minimum satisfaction probability of the timing constraint. A timing constraint is violated if the confidence threshold is not reached by the timed event trace. We present a ptime monitoring algorithm for detecting timing violation by finding the earliest expiration time (EET) of the deadline timer for each of the cases P = 100%, 50% ≤ P < 100%, and 0% < P < 50%, where P is the confidence threshold of the timing constraint. We give a derivation of the implicit constraints needed for computing the EET, and we show how to use an all-pairs shortest path algorithm to compute the implicit constraints.

Published in:

Real-Time Systems Symposium, 2003. RTSS 2003. 24th IEEE

Date of Conference:

3-5 Dec. 2003