Linear time-varying (max, +) representation of conflicting timed event graphs

Timed Event Graphs (TEGs) are a specific class of Petri nets that have been thoroughly studied given their useful linear state representation in (Max,+) algebra. Unfortunately, TEGs are generally not suitable for modeling systems displaying resources sharing (or conflicts). In this paper, we show that if a system with conflicts is modeled using an extended class of TEGs: Conflicting Timed Event Graphs (CTEGs), then it is quite possible to obtain an equivalent (Max,+) representation. More precisely, we prove that the evolution of a CTEG satisfies linear time-varying (Max,+) equations. In case of cyclic CTEGs, which are a natural model of many repetitive systems, we provide a standard time-invariant (Max,+) representation. Finally, a practical example (a Jobshop) is used for illustration to exhibit the interest of this investigation.