Synthesis of asynchronous controllers using integer linear programming

A novel strategy for the logic synthesis of asynchronous control circuits is presented. It is based on the structural theory of Petri nets and integer linear programming. Techniques that are capable of checking implementability conditions, such as complete state coding, and deriving a gate netlist to implement the specified behavior are presented. These techniques can handle Petri net specifications consisting of several thousands of transitions and provide a significant speed-up compared with techniques that have previously been proposed.Peer ReviewedPostprint (published version

Conflict Equivalence of Branching Processes

International audienceFor concurrent and large systems, specification step is a crucial point. Combinatory explosion is a limit that can be encountered when a state space exploration is driven on large specification modeled with Petri nets. Considering bounded Petri nets, technics like unfolding can be a way to cope with this problem. This paper is a first attempt to present an axiomatic model to produce the set of processes of unfoldings into a canonic form. This canonic form allows to define a conflict equivalence

Unfolding-based Partial Order Reduction

Partial order reduction (POR) and net unfoldings are two alternative methods to tackle state-space explosion caused by concurrency. In this paper, we propose the combination of both approaches in an effort to combine their strengths. We first define, for an abstract execution model, unfolding semantics parameterized over an arbitrary independence relation. Based on it, our main contribution is a novel stateless POR algorithm that explores at most one execution per Mazurkiewicz trace, and in general, can explore exponentially fewer, thus achieving a form of super-optimality. Furthermore, our unfolding-based POR copes with non-terminating executions and incorporates state-caching. Over benchmarks with busy-waits, among others, our experiments show a dramatic reduction in the number of executions when compared to a state-of-the-art DPOR.Comment: Long version of a paper with the same title appeared on the proceedings of CONCUR 201

Mining structured Petri nets for the visualization of process behavior

Visualization is essential for understanding the models obtained by process mining. Clear and efficient visual representations make the embedded information more accessible and analyzable. This work presents a novel approach for generating process models with structural properties that induce visually friendly layouts. Rather than generating a single model that captures all behaviors, a set of Petri net models is delivered, each one covering a subset of traces of the log. The models are mined by extracting slices of labelled transition systems with specific properties from the complete state space produced by the process logs. In most cases, few Petri nets are sufficient to cover a significant part of the behavior produced by the log.Peer ReviewedPostprint (author's final draft

Verifizierbare Entwicklung eines satellitenbasierten Zugsicherungssystems mit Petrinetzen

Nowadays model-based techniques are widely used in system design and development, especially for safety-critical systems such as train control systems. Given a design model, executable codes could be generated automatically from the model following certain transformation rules. A high-quality model of a system provides a good understanding, a favourable structure, a reasonable scale and abstraction level as well as realistic behaviours with respect to the concurrent operation of independent subsystems. Motivated by this principle, a first Coloured Petri Net (CPN) model of a satellite-based train control system (SatZB) with the capability of continuous simulation is developed employing the BASYSNET method which adopts Petri nets as the means of description during the whole development process. After establishing the system model, the verification tasks are identified based on the hazard analysis of the train control system. To verify the identified tasks for quality assurance, verification by means of simulation, formal analysis and testing is carried out considering the four representing system properties: function, state, structure and behaviour. For structural analysis, the concept of open nets is proposed to check the reproducibility of empty markings of scenario nets, the existence of dead transitions in the scenario nets, and the terminating states of the scenario nets. The system behaviour, in which states are involved, is investigated by reachability analysis. Unlike the conventional method of reachability analysis by calculating the state space of the Petri net, techniques based on Petri net unfoldings are introduced in this thesis. As to the functional verification, two model-based test generation techniques, i.e., CPN-based and SPENAT (Safe Place Transition Nets with Attributes)-based techniques, are presented. In this thesis, the proposed methods are exemplified by the application to the on-board module of SatZB model. According to the verification results, no errors were found in the module. Therefore, the confidence in the quality of the on-board module has been significantly increased.Heutzutage werden in zahlreichen Anwendungen modellbasierte Techniken zur Systementwicklung, insbesondere für sicherheitskritische Systeme wie Eisenbahnleit- und -sicherungssysteme, verwendet. Aus einem Design Modell kann dabei ausführbarer Code automatisch nach bestimmten Transformationsregeln generiert werden. Ein hochwertiges Modell des Systems bietet für die Entwicklung ein gutes Verständnis, eine günstige Struktur, eine angemessene Größenordnung und Abstraktionsebene als auch realistische Verhaltensweisen in Bezug auf den gleichzeitigen Betrieb von unabhängigen Subsystemen. Motiviert von dieses Prinzip wird ein erstes Farbige Petri-Netz (CPN)-Modell eines satellitenbasierten Zugsicherungssystem (SatZB) unter Verwendung der BASYSNET Methode entwickelt, der Petri-Netze als Beschreibungsmittel während des gesamten Entwicklungsprozesses nutzt. Dieses Modell bietet die Möglichkeit zur kontinuierlichen Simulation des Systemverhaltens. Nach der Erstellung des Systemmodells werden die Verifikationsaufgaben auf der Grundlage der Gefährdungsanalyse des Zugsicherungssystems identifiziert. Die abgeleiteten Bedingungen werden zur Qualitätssicherung durch Simulation, formale Analysen und Tests unter Berücksichtigung der vier Systemeigenschaften (Funktion, Zustand, Struktur und Verhalten) verifiziert. Für die Strukturanalyse wird das Konzept der offenen Netzen vorgeschlagen, um die Reproduzierbarkeit der leeren Markierungen der Szenario-Netze, die Existenz der Toten Transitionen in den Szenario-Netze, und die Abschluss Zustände der Szenario-Netze zu prüfen. Das Systemverhalten wird dabei durch Zustände beschrieben und durch eine Erreichbarkeitsanalyse untersucht. Im Gegensatz zu der konventionellen Methode, welche die Erreichbarkeit durch die Berechnung des Zustandsraums des Petri-Netzes analysiert, werden in dieser Arbeit Techniken auf Basis von Petri-Netz-Entfaltung eingeführt. Für die funktionale Verifikation werden zwei modellbasierte Testgenerierungstechniken, eine CPN-basierte und eine SPENAT (Sicheres Petrinetz mit Attributen)-basierte, vorgestellt. In dieser Arbeit werden die vorgeschlagenen Methoden durch die Anwendung auf das On-Board-Modul des SatZB-Modells veranschaulicht. Dabei wurden nach dem Abschluss der Prüfungen keine Fehler im Modul gefunden, wodurch das Vertrauen in die Qualität des On-Board-Moduls deutlich erhöht wurde

A Polynomial Translation of pi-calculus FCPs to Safe Petri Nets

We develop a polynomial translation from finite control pi-calculus processes to safe low-level Petri nets. To our knowledge, this is the first such translation. It is natural in that there is a close correspondence between the control flows, enjoys a bisimulation result, and is suitable for practical model checking.Comment: To appear in special issue on best papers of CONCUR'12 of Logical Methods in Computer Scienc