Applied Visual Anthropology

We study a new partial order semantics of Petri nets with read arcs, where read arcs model reading without consuming, which is often more adequate than the destructive-read-and-rewrite modelled in ordinary nets. As basic observations we take ST-traces, which are sequences of transition starts and ends. We define processes of our nets and derive two partial orders modelling causality and start precedence. These partial orders are related to observations and system states just as in the ordinary approach the single partial order of a process is related to firing sequences and reachable markings. Our approach also supports a new view of concurrency as captured by steps. 1 Introduction Describing the runs of a concurrent system by sequences of actions ignores the possible concurrency of these actions, which can be important e.g. for judging the temporal efficiency of the system. Alternatively to this so-called interleaving approach, one can take step sequences, where a step consists of si..