Knowledge, Timed Precedence and Clocks

This paper introduces a framework for knowledge-based analysis of issues of timing and clocks in systems with real-time constraints. We define the notion of timed precedence, a generalization of Lamport''s potential causality that is suitable for reasoning about timing in real-time systems. Knowledge about timed precedence is the key element in some of the work on optimal clock synchronization. We argue that the state of distributed knowledge, the natural candidate for use in such an analysis, is not appropriate for capturing various aspects of timing in real-time systems. We define an alternative notion, called inherent knowledge, which we find more appropriate. Finally, we illustrate how knowledge about the timed precedence of events can allow high-level reasoning about issues such as clock synchronization.

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