Specifying and verifying reactive systems in a multi-language environment

Abstract The multi-language environment Synchronie supports the design and formal verification of synchronous reactive systems. It integrates three synchronous languages and also three ways to specify properties: the temporal logic with future operators CTL, the temporal logic with past operators Past TL, and observers, which are particular synchronous programs. It is argued that this multi-language feature provides an answer to two major issues of formal verification: facility of formalizing properties and facility of verifying large systems. The approach is illustrated with the case study of a time-triggered protocol

How Much is worth to remember? A Taxonomy based on Petri Nets Unfoldings

The notion of unfolding plays a major role in the so called non sequential semantics of Petri nets, as well as in model checking of concurrent and distributed systems or in control theory. In literature various approaches to this notion have been proposed, where dependencies among events are represented either taking into account the whole history of the event (the so called individual token philosophy) or considering the whole history irrelevant (the so called collective token philosophy). In this paper we propose two unfoldings where the history is partially kept. These notions are based on unravelling a net rather than unfolding it. We compare them with the classical ones and we put all of them together in a coherent framework

Event Structures with Disabling/Enabling relation and Event Automata

In recent years the consideration that events in evolutions of concurrent systems can happen with different histories has received ground. In particular the possibility that part of the history can be abstracted away or identified, like in the collective tokens philosophy for Petri Nets, has gained the stage. The various brands of event structures considered in literature are tailored to a fixed interpretation with respect to the history of an event. We investigate the adequateness of event structures with a disabling/enabling relation, to settle a common ground for the history dependent and history independent interpretations, and we establish a relationship between event automata and these notions of event structures

Petri Nets Unfoldings and the individual/collective token philosophy

The notion of unfolding plays a major role in the so called non sequential semantics of Petri nets. In literature various approaches to this notion have been proposed, taking into account the so called individual token philosophy (the whole history is relevant) and the so called collective token philosophy (part of the history can be forgotten). In this paper we compare and relate two notions of unfolding (one for the individual and the other for the collective token philosophy) and we investigate on the relations between these two approaches and the non sequential behaviour of Petri Nets

Characterizing workflow nets using regions

The target of workflow mining is to obtain a workflow management systems from a possibly complete set of event logs of the system. This gives a fruitful support for developing complex business transaction sequences and business collaboration applications, possibly filling the gap from the theoretical design and the real instances. An algorithm (the alpha-algorithm) has been proposed in literature to rediscover a Workflow (Petri) Net that generated a given event log. This algorithm have some drawback as it fails in rediscovering the correct net. We investigate on how the theory of regions, used to synthesize nets from marking graphs, can be used to mine Workflow Nets, discussing the behaviour of region based net synthesis on some cases that turn out to be problematic for the alpha-algorithm. We also briefly discuss on how transitions systems can be obtained by event logs

Process discovery and Petri nets

The aim of the research domain known as process mining is to use process discovery to construct a process model as an abstract representation of event logs. The goal is to build a model (in terms of a Petri net) that can reproduce the logs under consideration, and does not allow different behaviours compared with those shown in the logs. In particular, process mining aims to verify the accuracy of the model design (represented as a Petri net), basically checking whether the same net can be rediscovered. However, the main mining methods proposed in the literature have some drawbacks: the classical α-algorithm is unable to rediscover various nets, while the region-based approach, which can mine them correctly, is too complex. In this paper, we compare different approaches and propose some ideas to counter the weaknesses of the region-based approach

Comparing Truly Concurrent Semantics for Contextual Place/Transition Nets with Inhibitor and Read Arcs

The paper is centered around the study and comparison of truly concurrent semantics for P/T nets with inhibitor and read arcs (called henceforth contextual P/T nets). We start proposing a causal semantics for P/T nets, that we prove to be equivalent to history preserving bisimulation defined on nonsequential processes. Then we develop a conservative extension of the causal semantics to contextual P/T nets and we prove this one to be finer than step semantics. Finally, a comparison of causal semantics with the process based semantics for contextual P/T systems proposed in [7] is carried out