Petri Net

The deployment of Worko w Management systems is a time- consuming and error-prone task. A possible solution is process min- ing, which automatically extracts worko w models from event-data logs. However, the current research in process mining still has problems in mining some common constructs in worko w models. Among these con- structs are short loops, which are loops of

This paper presents a process of systematization and analysis of the reliability parameters of a proportional hydraulic platform that aims to study position control using hydraulic systems. Currently the positioning systems using hydraulic circuits include mechanical and electronic components and software. These automatic systems involve diverse and complex technologies, for which reason the reliability analysis is difficult. Moreover, the failure modes which can occur in each item can produce distinct effects, increasing the complexity of this analysis. The control of all parameters involved becomes very difficult for the design agents, with consequences for the other phases of the life cycle. In this regard a methodology to systemize the information necessary to obtain a product with reliability is proposed. In this process, hierarchic FTA and FMEA diagrams are used as tools for the systematization of the reliability parameters, and Petri Nets are is used to represent the states a...

The importance of communication, information sharing and interoperability in an emergency response scenario have risen recently based on the frequency of disasters throughout the world and the wide range of severities and degrees of impacts. This work contributes to the area of emergency response communication qualitatively by presenting a systematic approach to develop an organizational communication model to improve overall emergency response. Establishing and accessing a reliable communication infrastructure at crisis is crucial in order to have accurate and real-time exchange of information. This work identifies a set of potential network oriented problems in existing inter-organizational communication protocols incorporating the information collected at several drill participations and interviewing the first responders. We conquer the complexity of a large, unique and unpredictable emergency response process by a top-down approach. We are constructing a high-level hierarchical ...

This invited paper presents a number of correlated specifications of example railway system problems. They use a variety of partially or fully integrated formal specification. The paper thus represents a mere repository of what we consider interesting case studies. The existence of the Unified Modeling Language [10, 67, 36, 20] has caused, for one reason or another, the research community to try formalise one or another facet of UML. In this paper we report on another way to achieve what UML attempts to achieve: Broadness of application, convenience of notation, and multiplicity of views. Whether these different UML views are unified, integrated, correlated or merely co-located is for others to dispute. We also seek to support multiple views, but are also in no doubt that there must be sound, well defined relations between such views. We thus report on ways and means of integrating formal techniques such as RAISE (RSL) [58, 59],

There exists ample literature on Petri nets and its potential in the modelling, analysis, synthesis and implementation of systems in the manufacturing applications domain (see for example [54, 15, 18]; moreover, in [65] an important bibliography is presented). This paper provides an examples-driven perspective. Nevertheless, not only complete examples from the application domain are considered. Manufacturing systems are frequently large systems, and conceptual complexity often appears because of some particular "local" constructions. The examples considered in this selected tour try to introduce in a progressive way some applied concepts and techniques. The starting point is an assembly cell, for which models concerning several phases of the design life-cycle are presented. Afterwards, some pull control and kanban management strategies are modelled. Then, two coloured models of production lines are presented. After that, a manufacturing system with two cells is modelled, and the difficulty of the practical analysis is shown. For very populated manufacturing systems or systems with high cadence, relaxation of discrete event models leads to hybrid and continuous approximations, an example of which will be introduced.

Purpose -The purpose of this paper is to present a new generic Petri net (PN) model based on assembly plan for assembly sequence optimization. The model aims to allow modeling the flexible assembly system (FAS) configuration, determining the optimal work in process, lead time, throughput, and utilization of each station. Moreover, it aims to show assembly features (AFs) as being useful in assembly sequence planning. Design/methodology/approach -Sophisticated knowledge of AFs is used to get very few feasible assembly sequences (ASs) rather than all possible ASs for a product. A PN model is developed to find out the near optimal assembly sequence out of the sequences obtained from the AF knowledge. It is also used for design and performance evaluation of FAS. Multiple optimization criteria are used for assembly sequence optimization, keeping in view the line balancing. The PN is optimized using weighted-WIP when the throughput is bounded by the utilization of the bottleneck machines. Findings -The results achieved from the example show a considerable reduction in the number of feasible ASs for a product. The PN optimization gives minimum WIP corresponding to the maximum production rate. Moreover, the PN model pushes more inventories to the initial assembly phase.

We have recently proposed an extension to Petri nets in order to be able to directly deal with all aspects of embedded digital systems. This extension is meant to be used as an internal model of our co-design environment. After analyzing relevant related work, and presenting a short introduction to our extension as a background material we describe the details

While the goal of verification is to check whether a model of the system under consideration has a desired property, supervisory control achieves correctness by adding a so-called supervisor that prevents the occurrence of incorrect behaviors to the original system. Supervisory control methods are appealing because they can be much more tractable than the corresponding verification problems. Here we first examine two supervisory control algorithms, one for enforcing mutual exclusion properties and the other for enforcing real-time deadlines on Petri net models of the controlled system. Next, we argue that use of supervisory control methods may lead to a simpler and more effective coding style for embedded software than current practices. Finally, we highlight research issues that must be addressed in order to permit widespread application of supervisory control methods.

Policies are increasingly used to manage large-scale distributed system. They usually adopt ECA rules that can 't express system i state transitions, enable policy servers to perform jlexible actions or cooperate eflciently. In this paper; a logic-based policy definition language LPDL is proposed. We define LPDL'S syntax, execution model and its semantic that provides a formal framework for policy-based network management. LPDL is proved to have Petri Net i expressive power and Turing Machine b computing power. Administrator can use LPDL to describe system b analysis and decision functions or encapsulate them into physical codes jlexibly based on actual need. Finally, a Cooperative Network Management Framework ( C N W ) , its protoqpe and application are presented to show that LPDL can meet the requirements of network management j. dynamic growth.

State of the art information system commonly record events in log files, also known as audit trails. Moreover, business processes often go beyond the sole recording the events and base decisions on the events observed in the past. To model such processes we extend the basic Petri net framework with the notion of history by associating tokens with histories, adding guards evaluated on the history to the transitions and mapping arcs to expressions involving histories. Guards and arc expressions can involve data associated with the ...

This paper deals with the modelling of batch systems by means of high-level Petri nets. Batch systems are systems that transform a continuous raw material through continuous equipment (as heat exchanger for example) and batch equipment (for instance, batch reactor). These systems are frequently used by chemical of food industry. Batch systems deal with concurrent activities and resource allocation mechanism.

Giving students suitable feedback information is one of the research issues in CAI. This research tries to evaluate if feedback did help in the course. For this purpose, this paper constructs an e-learning environment with feedback mechanism based on the previous research . Students' learning activity will be recorded by the system and suitable feedback will be sent to students via short message or e-mail. There are four fifth grade classes participated the experiment. The experiment analysis contains two parts, the first one is evaluating the feedback efficiency for all groups; and the second part separates the students into three clusters based on their academic achievement.

... 1 Introduction Modem e-business applications are often based on highly distributed, multi-tiered architectures compris-ing multiple ... rea-world e-business application and showing how QPN models could be exploited for performance analysis and prediction in capacity ...

Abstract Programmable Logic Controllers (PLC) have been used in industrial environment to control several different tasks. Such devices can be programmed using one of the languages specified in the IEC 61131–3 standard, such as Ladder or Functional Logic ...

In flexible manufacturing systems (FMS), each job is formed of a set of operations that should be executed consecutive. Determining the sequence of operations and assigning proper machine to each operation are two important problems in scheduling FMS's. This is an NP-hard problem. Recently using heuristic methods, numerous algorithms are presented for solving this problem. In this paper for scheduling of flexible manufacturing systems, a new algorithm called hybrid genetic algorithm-Petri net (HGA-PN) is presented using timed Petri net and combinational genetic algorithm. In our purposed algorithm, first the flexible manufacturing system is modeled by using timed Petri net, and then an appropriate scheduling is manufactured using combinational genetic algorithm. The experimental results illustrates that our proposed algorithm has higher efficiency over other existing algorithms.

The fusion of mechatronics, communication, control and information technologies has allowed the introduction of new automation paradigms into the production environment. The virtualization of the production environment facilitated by the application of the service-oriented architecture paradigm is one of major outcomes of that fusion. On one side, service-oriented automation works based on exposition, subscription and use of automation functions represented by e.g. web services. On the other side, the evolution of traditional industrial systems, particularly in the production area, as a response to architectural and behavioural (functional) viewpoints of the ISA95 enterprise architecture, where a close inter-relation between SCADA, DCS and MES systems facilitate the management and control of the production environment. Automation functions are increasingly performed by the composition and orchestration of services. Among other methods, the application of formal Petri net based orchestration approaches is being industrially established. This paper presents the major characteristics that such a Petri net based orchestration presents when it is developed, implemented and deployed in an industrial environment.

Queueing Petri nets are a powerful formalism that can be exploited for modeling distributed systems and analyzing their performance and scalability. By combining the modeling power and expressiveness of queueing networks and stochastic Petri nets, queueing Petri nets provide a number of advantages. In this paper, we present Version 2.0 of our tool QPME (Queueing Petri net Modeling Environment) for modeling and analysis of systems using queueing Petri nets. The development of the tool was initiated by Samuel Kounev in 2003 at the Technische Universität Darmstadt in the group of Prof. Alejandro Buchmann. Since then the tool has been distributed to more than 100 organizations worldwide. QPME provides an Eclipse-based editor for building queueing Petri net models and a powerful simulation engine for analyzing the models. After presenting the tool, we discuss ongoing work on the QPME project and the planned future enhancements of the tool.

This paper focuses on the resolution of the reachability problem in Petri nets, using the mathematical programming paradigm. The proposed approach is based on an implicit traversal of the Petri net reachability graph. This is done by constructing a unique sequence of Steps that represents exactly the total behaviour of the net. We propose several formulations based on integer and/or binary linear programming, and the corresponding sets of adjustments to the particular class of problem considered. Our models are validated on a set of benchmarks and compared with standard approaches from IA and Petri nets community.

A formal modeling technique, based on colored timed Petri net and UML static structure modeling languages is used to teach students to model their business process problem as a discrete event system, before they build a working simulation model in a simulation tool (in our case Arena). Combining Petri net and UML static structure diagrams, one can build an abstract, well defined and complete model. This model enables the simulation analyst to make an unambiguous, complete and yet easily readable model of the target operational process. The two most important classes of decisions that are reflected in the conceptual model are the choice of the real world details to be taken in or left out the model and the precise specification of the output parameters of the simulation. This paper describes the modeling technique and discusses its value in teaching and in the formulation of decision problems regarding operational processes.

This paper is devoted both to the study of observability criteria and the design of observers in the continuous Petri net setting. The concept of structural observability, regarding the possibility of estimating the marking of places, i.e., the system state, for any speed of the transitions is introduced and studied for the subclass of join-free Petri nets (JF). For non-join-free Petri nets, conditions to compute suitable state estimates are established. The proposed observers are piecewise linear systems that assure the continuity of the estimate even when a switch occurs. The system simulation may allow us to estimate even the unobservable space of the net system during a given time period.

Petri nets (PN) are useful for the modelling, analysis and control of hybrid dynamical systems (HDS) because PN combine in a comprehensive way discrete events and continuous behaviours. On one hand, PN are suitable for modelling the discrete part of HDS and for providing a discrete abstraction of continuous behaviours. On the other hand, continuous PN are suitable for modelling the continuous part of HDS and for working out a continuous approximation of the discrete part in order to avoid the complexity associated with the exponential growth of discrete states. This paper focuses on the advantages of PN as a modelling tool for HDS. Investigations of such models for diagnosis and control issues are detailed.

Due to their complexity, nowadays it is virtually unconceivable to design and implement large digital systems without the use of computer-aided design tools. Many petri net extensions have been proposed aiming at describing hardware characteristics as accurately as possible. Among all petri net extensions developed for use with digital systems, only two of them have nearly all characteristics needed to describe such systems in full. They are place chart nets, and petri nets for embedded systems. Using the latter as an example we discuss some issues that may improve the capability of petri nets in dealing with digital systems.

In this paper, we present our methodology proposal for cooperative remote systems modeling. Its aim is to develop models of existing or planned cooperative systems. These models are used to specify systems or to create dynamic working simulations. Comparative performances are deduced from the latter. The associated meta-model proposal is based, among other things, on the use of multi-agent systems, Petri nets and stochastics Petri nets. After having described the whole methodology concepts, we show a set of general results extracted from simulations.

paper presents a formal approach to threat-driven modeling and verification of secure software using aspect-oriented Petri nets. Based on the behavior model of intended functions, we identify and build formal models of security threats, which are potential misuses and anomalies of the intended functions that violate security goals. Threat mitigations are further modeled in an aspect-oriented paradigm. Taking Petri nets

The increasing number of Petri net variants naturally leads to the question whether the term "Petri net" is more than a common name for very different concepts. This contribution tries to identify aspects common to all or at least to most Petri nets. It concentrates on those features where Petri nets significantly differ from other modeling languages, i.e. we ask where the use of Petri nets leads to advantages compared to other languages. Different techniques that are usually comprised under the header "analysis" are distinguished with respect to the analysis aim. Finally, the role of Petri nets in the development of distributed systems is discussed.

Last time we reported on Romeo, analyses with this tool were mostly based on translations to other tools. This new version provides an integrated TCTL model-checker and has gained in expressivity with the addition of parameters. Although there exists other tools to compute the state-space of stopwatch models, Romeo is the first one that performs TCTL model-checking on stopwatch models. Moreover, it is the first tool that performs TCTL model-checking on timed parametric models. Indeed, Romeo now features an efficient model-checking of time Petri nets using the Uppaal DBM Library, the model-checking of stopwatch Petri nets and parametric stopwatch Petri nets using the Parma Polyhedra Library and a graphical editor and simulator of these models. Furthermore, its audience has increased leading to several industrial contracts. This paper reports on these recent developments of Romeo.

In this paper we deal with the problem of estimating the marking of a labeled Petri net system based on the observation of transitions labels. In particular, we assume that a certain number of transitions are labeled with the empty string ε, while a different label taken from a given alphabet is assigned to all the other transitions. Transitions labeled with the empty string are called silent because their firing cannot be observed. Under some technical assumptions on the structure of the Tε -induced subnet, where Tε denotes the set of silent transitions, we formally prove that the set of markings consistent with the observed word can be represented by a linear system with a fixed structure that does not depend on the length of the observed word.

The International Standard on Petri nets, ISO/IEC 15909, provides a formal semantics and syntax to enable model interchange and industrial dissemination. Part 2 defines a concrete interchange format as an XML-based language: PNML. This language is bound to evolve together with future developments of the standard.

The software Petri Net Toolbox, dealing with Petri nets under MATLAB, is presented. It can handle five types of Petri nets (untimed, transition-timed, place-timed, stochastic and generalized stochastic) with finite or infinite capacity. The toolbox is equipped with a user-friendly graphical interface and allows three simulation modes accompanied or not by animation. Its functions cover the key topics of analysis such as coverability tree, structural properties (including invariants), time-dependent performance indices, max-plus state-space representations. A design procedure is also available, based on parameterized models. The integration with the MATLAB philosophy enlarges the utilization of this popular software towards the area of discrete-event systems. The applicability of this toolbox in several domains of engineering, illustrated by three examples, demonstrates its value as an educational aid.

ISO/IEC 15909-2 International Standard defines a universal XML-based transfer syntax for Petri nets. The main objective of this exchange format, namely Petri Net Markup Language (PNML), is to enable compatibility and interoperability among heterogeneous Petri net tools, while keeping expressiveness and extensibility. Hence, it shall support different types of Petri nets and be extensible to allow for future types. To make it applicable and integrable at low cost to existing tools, a software framework is proposed to the Petri net community. This framework enables fast and cost-effective tools adaptation to PNML use by bringing forth model engineering techniques through model transformation, backed on OMG's Model-Driven Architecture principles. This paper shows that the proposed approach is concerned for compliance with the standard, enhancing compatibility between tools. It is realistic and pragmatic. It copes with extensibility issues by allowing fast re-engineering, thanks to model-driven development approach and code generation.

After a survey of some approaches for modeling hybrid systems by means of Petri nets (t-time Petri nets, colored Petri nets, hybrid Petri nets and differential predicate transition nets), this paper illustrates how these formal models can be used for simulation and validation. It is shown how it was possible to use aggregated qualitative models concurrently with detailed ones.

It is a great challenge to effectively manage automated manufacturing systems in which automated guided vehicles (AGVs) are adopted to handle materials, because of such features as prior unknown AGV requests and changing AGV initial positions. This paper aims to find the shortest time routes, while both deadlock and blocking in AGV systems are avoided. It first finds the shortest routes based on a guide path layout, and then performs rerouting, whenever necessary, to avoid deadlock and blocking according to a deadlock avoidance policy, previously developed by the authors. The proposed approach can offer better solutions than existing methods. For some cases, it can find a solution, while the existing ones cannot.

Agile and flexible manufacturing system makes it mandatory that a control program should have a features such as agility, flexibility, and reusability in order to meet fast changing customer demands. Proper modeling and fast formation of the control logics using graphical and mathematical tools is one of the most peculiar ways to make the control logic more feasible for rapid product prototyping, concurrent engineering, flexible, and agile manufacturing. This paper illustrates efficient conversion of Petri nets model into programmable logic controller like LLD (Ladder Logic Diagram) in a very convenient way using one-to-one mapping technique. Furthermore, property analysis has been briefly explained to generate flawless control code for better operational performance. An example of painting robots has been demonstrated to prove the proposed method.

Contemporary workflow management systems are driven by explicit process models, i.e., a completely specified workflow design is required in order to enact a given workflow process. Creating a workflow design is a complicated time-consuming process and, typically, there are discrepancies between the actual workflow processes and the processes as perceived by the management. Therefore, we have developed techniques for discovering workflow models. The starting point for such techniques is a so-called "workflow log" containing information about the workflow process as it is actually being executed. We present a new algorithm to extract a process model from such a log and represent it in terms of a Petri net. However, we will also demonstrate that it is not possible to discover arbitrary workflow processes. In this paper, we explore a class of workflow processes that can be discovered. We show that the -algorithm can successfully mine any workflow represented by a so-called SWF-net.

Computer Automated Multi-Paradigm Modelling (CAM-PaM) is an enabler for domain-specific analysis and design. Traffic, a new untimed visual formalism for vehicle traffic networks, is introduced. The syntax of Traffic models is meta-modelled in the Entity-Relationship Diagrams formalism. From this, augmented with concrete syntax information, a visual modelling environment is synthesized using our CAMPaM tool AToM 3 , A Tool for Multi-formalism and Meta-Modelling. The semantics of the Traffic formalism is subsequently modelled by mapping Traffic models onto Petri Net models. As models' abstract syntax is graph-like, graph rewriting can be used to transform models. The advantages of a domain-specific formalism such as Traffic as opposed to a generic formalism such as Petri Nets are presented. We demonstrate how mapping onto Petri Nets allows one to employ the vast array of Petri Net analysis techniques. A Coverability Graph is generated and conservation analysis is automated by transforming this graph into an Integer Linear Programming specification.

This paper focuses on the use of Petri nets (PN) to model the control of signalized intersections. The application of PN to an eight-phase traffic signal controller is illustrated. Structural analysis of the control PN model is performed to demonstrate how the model enforces the traffic operation safety rules. This is followed by a discussion of why this modeling tool has future value as the use of more advanced control strategies continue to expand.