Observers for Timed DESs With Observation Delays and Losses

Abstract

This article is about observation and states estimation for timed discrete event systems with observation delays and losses. This topic is particularly important for networked discrete event systems. On the one hand, in order to explicitly incorporate timing aspects, labeled timed automata under specific time semantics with a single clock and time interval constraints are used at the modeling level. On the other hand, delays and losses in observations sequences are specified according to delayed observable events and a set of release locations where the delayed observations are outputted. This release observation mechanism is added to the timing specifications and the resulting model is transformed into clock interval automata with release mechanism for which determinization is obtained as an extension of the untimed reasoning by representing observation of the advance of time with a one time unit tick event. Our main motivation for this research is to show how the time information and the release of delayed observations both refine the analysis of information flow. Potential applications to safety and privacy issues are discussed.