Dynamic state reconciliation and model-based fault detection for chemical processes

In this paper, we present a method for the fault detection based on the residual generation. The main idea is to reconstruct the outputs of the system from the measurements using the extended Kalman filter. The estimations are compared to the values of the reference model and so, deviations are interpreted as possible faults. The reference model is simulated by the dynamic hybrid simulator, PrODHyS. The use of this method is illustrated through an application in the field of chemical processe

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

Tackling Dierent Business Process Perspectives

Business Process Management (BPM) has emerged as a discipline to design, control, analyze, and optimize business operations. Conceptual models lie at the core of BPM. In particular, business process models have been taken up by organizations as a means to describe the main activities that are performed to achieve a specific business goal. Process models generally cover different perspectives that underlie separate yet interrelated representations for analyzing and presenting process information. Being primarily driven by process improvement objectives, traditional business process modeling languages focus on capturing the control flow perspective of business processes, that is, the temporal and logical coordination of activities. Such approaches are usually characterized as \u201cactivity-centric\u201d. Nowadays, activity-centric process modeling languages, such as the Business Process Model and Notation (BPMN) standard, are still the most used in practice and benefit from industrial tool support. Nevertheless, evidence shows that such process modeling languages still lack of support for modeling non-control-flow perspectives, such as the temporal, informational, and decision perspectives, among others. This thesis centres on the BPMN standard and addresses the modeling the temporal, informational, and decision perspectives of process models, with particular attention to processes enacted in healthcare domains. Despite being partially interrelated, the main contributions of this thesis may be partitioned according to the modeling perspective they concern. The temporal perspective deals with the specification, management, and formal verification of temporal constraints. In this thesis, we address the specification and run-time management of temporal constraints in BPMN, by taking advantage of process modularity and of event handling mechanisms included in the standard. Then, we propose three different mappings from BPMN to formal models, to validate the behavior of the proposed process models and to check whether they are dynamically controllable. The informational perspective represents the information entities consumed, produced or manipulated by a process. This thesis focuses on the conceptual connection between processes and data, borrowing concepts from the database domain to enable the representation of which part of a database schema is accessed by a certain process activity. This novel conceptual view is then employed to detect potential data inconsistencies arising when the same data are accessed erroneously by different process activities. The decision perspective encompasses the modeling of the decision-making related to a process, considering where decisions are made in the process and how decision outcomes affect process execution. In this thesis, we investigate the use of the Decision Model and Notation (DMN) standard in conjunction with BPMN starting from a pattern-based approach to ease the derivation of DMN decision models from the data represented in BPMN processes. Besides, we propose a methodology that focuses on the integrated use of BPMN and DMN for modeling decision-intensive care pathways in a real-world application domain

Recent advances in petri nets and concurrency

CEUR Workshop Proceeding

The Impact of Petri Nets on System-of-Systems Engineering

The successful engineering of a large-scale system-of-systems project towards deterministic behaviour depends on integrating autonomous components using international communications standards in accordance with dynamic requirements. To-date, their engineering has been unsuccessful: no combination of top-down and bottom-up engineering perspectives is adopted, and information exchange protocol and interfaces between components are not being precisely specified. Various approaches such as modelling, and architecture frameworks make positive contributions to system-of-systems specification but their successful implementation is still a problem. One of the most popular modelling notations available for specifying systems, UML, is intuitive and graphical but also ambiguous and imprecise. Supplying a range of diagrams to represent a system under development, UML lacks simulation and exhaustive verification capability. This shortfall in UML has received little attention in the context of system-of-systems and there are two major research issues: 1. Where the dynamic, behavioural diagrams of UML can and cannot be used to model and analyse system-of-systems 2. Determining how Petri nets can be used to improve the specification and analysis of the dynamic model of a system-of-systems specified using UML This thesis presents the strengths and weaknesses of Petri nets in relation to the specification of system-of-systems and shows how Petri net models can be used instead of conventional UML Activity Diagrams. The model of the system-of-systems can then be analysed and verified using Petri net theory. The Petri net formalism of behaviour is demonstrated using two case studies from the military domain. The first case study uses Petri nets to specify and analyse a close air support mission. This case study concludes by indicating the strengths, weaknesses, and shortfalls of the proposed formalism in system-of-systems specification. The second case study considers specification of a military exchange network parameters problem and the results are compared with the strengths and weaknesses identified in the first case study. Finally, the results of the research are formulated in the form of a Petri net enhancement to UML (mapping existing activity diagram elements to Petri net elements) to meet the needs of system-of-systems specification, verification and validation

Formal techniques for the procedural control of industrial processes

Imperial Users onl

Combining SysML and Timed Coloured Petri Nets for Designing Smart City Applications

A smart city is an urban centre that integrates a variety of solutions to improve infrastructure performance and achieve sustainable urban development. Urban roads are a crucial infrastructure highly demanded by citizens and organisations interested in their deployment, performance, and safety. Urban traffic signal control is an important and challenging real-world problem that aims to monitor and improve traffic congestion. The deployment of traffic signals for vehicles or pedestrians at an intersection is a complex activity that changes constantly, so it is necessary to establish rules to control the flow of vehicles and pedestrians. Thus, this article describes the joint use of the SmartCitySysML, a profile proposed by the authors, with TCPN (Timed Coloured Petri Nets) to refine and formally model SysML diagrams specifying the internal behaviour, and then verify the developed model to prove behavioural properties of an urban traffic signal control system

Verification of soundness and other properties of business processes

In this thesis we focus on improving current modeling and verification techniques for complex business processes. The objective of the thesis is to consider several aspects of real-life business processes and give specific solutions to cope with their complexity. In particular, we address verification of a proper termination property for workflows, called generalized soundness. We give a new decision procedure for generalized soundness that improves the original decision procedure. The new decision procedure reports on the decidability status of generalized soundness and returns a counterexample in case the workflow net is not generalized sound. We report on experimental results obtained with the prototype implementation we made and describe how to verify large workflows compositionally, using reduction rules. Next, we concentrate on modeling and verification of adaptive workflows — workflows that are able to change their structure at runtime, for instance when some exceptional events occur. In order to model the exception handling properly and allow structural changes of the system in a modular way, we introduce a new class of nets, called adaptive workflow nets. Adaptive workflow nets are a special type of Nets in Nets and they allow for creation, deletion and transformation of net tokens at runtime and for two types of synchronizations: synchronization on proper termination and synchronization on exception. We define some behavioral properties of adaptive workflow nets: soundness and circumspectness and employ an abstraction to reduce the verification of these properties to the verification of behavioral properties of a finite state abstraction. Further, we study how formal methods can help in understanding and designing business processes. We investigate this for the extended event-driven process chains (eEPCs), a popular industrial business process language used in the ARIS Toolset. Several semantics have been proposed for EPCs. However, most of them concentrated solely on the control flow. We argue that other aspects of business processes must also be taken into account in order to analyze eEPCs and propose a semantics that takes data and time information from eEPCs into account. Moreover, we provide a translation of eEPCs to Timed Colored Petri nets in order to facilitate verification of eEPCs. Finally, we discuss modeling issues for business processes whose behavior may depend on the previous behavior of the process, history which is recorded by workflow management systems as a log. To increase the precision of models with respect to modeling choices depending on the process history, we introduce history-dependent guards. The obtained business processes are called historydependent processes.We introduce a logic, called LogLogics for the specification of guards based on a log of a current running process and give an evaluation algorithm for such guards. Moreover, we show how these guards can be used in practice and define LogLogics patterns for properties that occur most commonly in practice

Sixth Workshop and Tutorial on Practical Use of Coloured Petri Nets and the CPN Tools Aarhus, Denmark, October 24-26, 2005

This booklet contains the proceedings of the Sixth Workshop on Practical Use of Coloured Petri Nets and the CPN Tools, October 24-26, 2005. The workshop is organised by the CPN group at the Department of Computer Science, University of Aarhus, Denmark. The papers are also available in electronic form via the web pages: http://www.daimi.au.dk/CPnets/workshop0