Showing papers on "Process architecture published in 2012"

Snoopy --- a unifying petri net tool

Abstract: The tool Snoopy provides a unifying Petri net framework which has particularly many application scenarios in systems and synthetic biology. The framework consists of two levels: uncoloured and coloured. Each level comprises a family of related Petri net classes, sharing structure, but being specialized by their kinetic information. Petri nets of all net classes within one level can be converted into each other, while changing the level involves user-guided folding or automatic unfolding. Models can be hierarchically structured, allowing for the mastering of larger networks. Snoopy supports the simultaneous use of several Petri net classes; the graphical user interface adapts dynamically to the active one. Built-in animation and simulation (depending on the net class) are complemented by export to various analysis tools. Snoopy facilitates the extension by new Petri net classes thanks to its generic design.

A New Approach for Diagnosability Analysis of Petri Nets Using Verifier Nets

Abstract: In this paper, we analyze the diagnosability properties of labeled Petri nets We consider the standard notion of diagnosability of languages, requiring that every occurrence of an unobservable fault event be eventually detected, as well as the stronger notion of diagnosability in K steps, where the detection must occur within a fixed bound of K event occurrences after the fault We give necessary and sufficient conditions for these two notions of diagnosability for both bounded and unbounded Petri nets and then present an algorithmic technique for testing the conditions based on linear programming Our approach is novel and based on the analysis of the reachability/coverability graph of a special Petri net, called Verifier Net, that is built from the Petri net model of the given system In the case of systems that are diagnosable in K steps, we give a procedure to compute the bound K To the best of our knowledge, this is the first time that necessary and sufficient conditions for diagnosability and diagnosability in K steps of labeled unbounded Petri nets are presented

Modeling and evaluation of stochastic Petri nets with TimeNET 4.1

Abstract: The paper presents a major update of the software tool TimeNET, a package for the modeling and performance evaluation of standard and colored stochastic Petri nets. Among its main characteristics are simulation and analysis modules for stationary and transient evaluation of Petri nets including non-exponentially distributed delays, as well as an efficient simulation module for complex colored models. An overview of the tool is given as well as a description of the new features, which are demonstrated using a manufacturing system application example. The tool is available free of charge for non-commercial use.

TAPAAL 2.0: integrated development environment for timed-arc petri nets

Abstract: TAPAAL 2.0 is a platform-independent modelling, simulation and verification tool for extended timed-arc Petri nets. The tool supports component-based modelling and offers an automated verification of the EF, AG, EG and AF fragments of TCTL via translations to Uppaal timed automata and via its own dedicated verification engine. After more than three years of active development with a main focus on usability aspects and on the efficiency of the verification algorithms, we present the new version of TAPAAL 2.0 that has by now reached its maturity and offers the first publicly available tool supporting the analysis and verification of timed-arc Petri nets.

A Hybrid Model of Complex Automated Warehouse Systems—Part I: Modeling and Simulation

Abstract: An automated warehouse system has two main components: an automated storage and retrieval subsystem consisting of a number of aisles, each one served by a crane, and a picking area which is formed by bays where stock units coming from the aisles are partially emptied by human operators. These two components are connected via an interface area consisting of carousels, conveyors, and buffers. This area is usually modeled as a discrete event system, while the overall system performance depends also on continuous time phenomena. Part I presents a hybrid model based on a new Petri net formalism that merges the concepts of Hybrid Petri Nets and Colored Petri Nets to obtain modular and compact models for these systems. An example is discussed in detail to motivate the introduction of a new formalism. A control oriented simulation tool is also presented. Part II will focus on the application of this formalism to automated warehouse systems analysis and performance evaluation. Finally, a real case study is considered to show the effectiveness of the approach.

Robot task plan representation by Petri nets: modelling, identification, analysis and execution

Abstract: In this paper we introduce a framework to represent robot task plans based on Petri nets. Our approach enables modelling a robot task, analysing its qualitative and quantitative properties and using the Petri net representation for actual plan execution. The overall model is obtained from the composition of simple models, leading to a modular approach. Analysis is applied to a closed loop between the robot controller and the environment Petri net models. We focus here on the quantitative properties, captured by stochastic Petri net models. Furthermore, we introduce a method to identify the environment and action layer parameters of the stochastic Petri net models from real data, improving the significance of the model. The framework building blocks and a single-robot task model are detailed. Results of a case study with simulated soccer robots show the ability of the framework to provide a systematic modelling tool, and of determining, through well-known analysis methods for stochastic Petri nets, relevant properties of the task plan applied to a particular environment.

Business process architecture: use and correctness

Abstract: Becoming more and more process oriented, companies develop collections of hundreds or even thousands of business process models that represent the complex system of cooperating entities that form an organization. Designing and analyzing the structure of this system of business process models emerges as a new challenge, which is covered by the field of business process architecture. This paper presents a formal conceptual framework for representing and analyzing business process architectures. It identifies patterns of relations between process models, and it introduces anti-patterns that represent erroneous relations between them. The conceptual framework and the patterns are evaluated using a real-world process model collection. The evaluation shows that explicitly representing and analyzing relations between process models can help improving the correctness and consistency of the business process architecture as a whole.

The Ordinal-Recursive Complexity of Timed-arc Petri Nets, Data Nets, and Other Enriched Nets

Abstract: We show how to reliably compute fast-growing functions with timed-arc Petri nets and data nets. This construction provides ordinal-recursive lower bounds on the complexity of the main decidable properties (safety, termination, regular simulation, etc.) of these models. Since these new lower bounds match the upper bounds that one can derive from wqo theory, they precisely characterise the computational power of these so-called "enriched" nets.

Report on the Model Checking Contest at Petri Nets 2011

Abstract: This article presents the results of the Model Checking Contest held within the SUMo 2011 workshop, a satellite event of Petri Nets 2011 This contest aimed at a fair and experimental evaluation of the performances of model checking techniques applied to Petri nets

A Hybrid Model of Complex Automated Warehouse Systems—Part II: Analysis and Experimental Results

Abstract: An automated warehouse system has two main components: an automated storage and retrieval subsystem consisting of a number of aisles, each one served by a crane, and a picking area which is formed by bays where stock units coming from the aisles are partially emptied by human operators. These two components are connected via an interface area consisting of carousels, conveyors and buffers. This area is usually modeled as a discrete event system, while the overall system performance depends also on continuous time phenomena. In Part I, a hybrid modeling approach based on a new Petri net formalism and a freeware simulation tool have been presented. The concepts of Hybrid Petri Nets and Colored Petri Nets are merged to obtain modular and compact models for automated warehouse systems. Part II now focuses on the application of this formalism to automated warehouse systems analysis and performance evaluation. Liveness analysis is performed by means of a hybrid automaton obtained from the net model. A deadlock prevention policy is synthesized working on an aggregated model. Finally, a real case study is considered to show the effectiveness of the approach.

Scheduling FMS with alternative routings using Petri nets and near admissible heuristic search.

Abstract: This paper proposes and evaluates a near admissible heuristic search strategy and its application to a kind of flexible manufacturing system (FMS) scheduling in a Petri net framework. Petri nets can concisely model the strict precedence constraint, multiple kinds of resources, and concurrent activities. To cope with the complexities for scheduling of FMS with alternative routings, this paper proposes an admissible heuristic function based on the execution of P-timed Petri nets and presents an improved dynamic weighting A* strategy using the proposed heuristic function. The search scheme does not need to predict the depth of solution in advance and the quality of the search result is also controllable. Some numerical experiments are carried out to demonstrate usefulness of the algorithm.

High-level Petri nets for the process description and control in service-oriented manufacturing systems

Abstract: The use of service-orientation principles in manufacturing systems is a promising solution to achieve modularity, flexibility, re-configurability and interoperability. Crucial issues in these service-oriented systems are the description and co-ordination of the execution of the services offered by the distributed entities. This paper introduces an integrated approach for the design, analysis, validation, simulation and process execution of service-oriented manufacturing systems, using the High-level Petri net formalism as the formal language to describe the system behaviour. The use of the proposed approach contributes to achieving an easier and faster development of these solutions and provides the basis to support modularity and re-configurability.

Petri nets and genetic algorithms for complex manufacturing systems scheduling

Abstract: In this paper we propose the GAPN (genetic algorithms and Petri nets) approach, which combines the modelling power of Petri nets with the optimisation capability of genetic algorithms (GAs) for manufacturing systems scheduling. This approach uses both Petri nets to formulate the scheduling problem and GAs for scheduling. Its primary advantage is its ability to model a wide variety of manufacturing systems with no modifications either in the net structure or in the chromosomal representation. In this paper we tested the performance on both classical scheduling problems and on a real life setting of a manufacturer of car seat covers. In particular, such a manufacturing system involves features such as complex project-like routings, assembly operations, and workstations with unrelated parallel machines. The implementation of the algorithm at the company is also discussed. Experiments show the validity of the proposed approach.

Transactions on Petri Nets and Other Models of Concurrency V

Abstract: Associated with a chemical reaction network is a natural labelled bipartite multigraph termed an SR graph, and its directed version, the DSR graph. These objects are closely related to Petri nets, but encode weak assumptions on the reaction kinetics, and are more generally associated with continuous-time, continuous-state models rather than discrete-event systems. The construction of SR and DSR graphs for chemical reaction networks is presented. Conclusions about asymptotic behaviour of the associated dynamical systems which can be drawn easily from the graphs are discussed. In particular, theorems on ruling out the possibility of multiple equilibria or stable oscillation based on computations on SR/DSR graphs are presented. These include both published and new results. The power and limitations of such results are illustrated via several examples. 1 Chemical Reaction Networks: Structure and Kinetics Models of chemical reaction networks (CRNs) are able to display a rich variety of dynamical behaviours [1]. In this paper, a spatially homogeneous setting is assumed, and the state of a CRN is defined to be the set of concentrations of the reactants involved, each a nonnegative real number. In addition, continuoustime models are treated, so that CRNs involving n chemicals give rise to local semiflows on R≥0, the nonnegative orthant in R . These local semiflows are fully determined if we know 1) the CRN structure, that is, which chemicals react with each other and in what proportions, and 2) the CRN kinetics, that is, how the reaction rates depend on the chemical concentrations. An important question is which CRN behaviours are determined primarily by reaction network structure, with limited assumptions about the kinetics. As will be seen below, a variety of representations of CRN structure are possible, for example via matrices or generalised graphs. Some of these representations encode weak assumptions on the reaction kinetics. Of these, a signed, labelled, bipartite multigraph, termed an SR graph, and its directed version, 1 The term derives from “species-reaction graph” [2]. However, while CRNs provided the original motivation for their construction, such graphs have since proved useful in more general contexts. The construction here follows [3]. K. Jensen, S. Donatelli, and J. Kleijn (Eds.): ToPNoC V, LNCS 6900, pp. 1–21, 2012. c © Springer-Verlag Berlin Heidelberg 2012

An efficient method for unfolding colored Petri nets

Abstract: Unfolding is an essential problem in reusing existing Petri net simulation and analysis techniques and related tools for colored Petri nets. We present an efficient unfolding method, in which we provide two approaches to efficiently compute transition instances. That is, for a transition, if the color set of each variable in its guard is a finite integer domain, a constraint satisfaction approach is used to obtain all valid transition instances; otherwise, a general algorithm is adopted, in which some optimization techniques like partial binding -- partial test and pattern matching are used. This method has been applied to unfold large-scale colored Petri nets, which has proven its efficiency.

On distributability of petri nets

Abstract: We formalise a general concept of distributed systems as sequential components interacting asynchronously. We define a corresponding class of Petri nets, called LSGA nets, and precisely characterise those system specifications which can be implemented as LSGA nets up to branching ST-bisimilarity with explicit divergence.

Ten years of saturation: a petri net perspective

Abstract: Due to their appealing conceptual simplicity and availability of computer tools for their analysis, Petri nets are widely used to model discrete-event systems in many areas of engineering. However, the computational resources required to carry out the analysis of a Petri net model are often enormous, hindering their practical impact. In this survey, we consider how symbolic methods based on the use of decision diagrams can greatly increase the size of Petri nets that an ordinary computer can reasonably tackle. In particular, we present this survey from the perspective of the efficient saturation method we proposed a decade ago, and introduce along the way the most appropriate classes of decision diagrams to answer important Petri net questions, from reachability to CTL model checking and counterexample generation, from p-semiflow computation to the solution of timed or Markovian nets.

Stochastic modeling and analysis using QPME: queueing petri net modeling environment v2.0

Abstract: 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 our tool QPME (Queueing Petri net Modeling Environment) for modeling and analysis using queueing Petri nets. QPME provides an Eclipse-based editor for building queueing Petri net models and a powerful simulation engine for analyzing these models. The development of the tool started in 2003 and since then the tool has been distributed to more than 120 organizations worldwide.

Web based IOPT Petri net Editor with an extensible plugin architecture to support generic net operations

Abstract: This paper presents a new Web based Petri net Editor employing AJAX principles to allow the interactive design and edition of Petri net models using standard Web browsers. The editor includes an integrated plug-in architecture to simplify the addition of generic net operations without requiring the manipulation of internal editor data-structures. IOPT-nets are a non-autonomous Petri net class targeting the model-based development of embedded system controllers and combine the well know properties of Petri nets with input and output signals and events to establish the communication of controllers with the external world. The editor is a part of the IOPT-tools Web service that also contains model-checking and automatic code-generation tools, supporting a complete model-based development work-flow, starting from model design to the final controller code generation. All tools are available at the research group Web page (http://gres.uninova.pt).

Introduction to queueing petri nets: modeling formalism, tool support and case studies

Abstract: Queueing Petri nets are a powerful formalism that can be exploited for modeling distributed systems and evaluating 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. This tutorial presents an introduction to queueing Petri nets first introducing the modeling formalism itself and then summarizing the results of several modeling case studies which demonstrate how queueing Petri nets can be used for performance modeling and analysis. As part of the tutorial, we present QPME (Queueing Petri net Modeling Environment), an open-source tool for stochastic modeling and analysis of systems using queueing Petri nets. Finally, we briefly present a model-to-model transformation automatically generating a queueing Petri net model from a higher-level software architecture model annotated with performance relevant information.

RECONNET: A Tool for Modeling and Simulating with Reconfigurable Place/Transition Nets

Abstract: In this contribution we present a tool for modeling and simulation with reconfigurable Petri nets. Taking the idea of algebraic graph transformations to marked Petri nets we obtain Petri nets whose net structure can be changed dynamically. The rule-based change of the net structure enables the adequate modeling of complex, dynamic structures as for example of the scenarios of the Living Place Hamburg. The tool \reconnet \ uses decorated place/transition nets that are extended by various annotations. Especially, they have transition labels that may change when the transition fires. The transformation approach is based on the well-known algebraic transformation approach, but here we use a variant, namely the cospan approach, that inverts the relation between left- and right-hand sides and interface in the rules.

Asynchronous-Channels and Time-Domains Extending Petri Nets for GALS Systems

Abstract: A specific class of Petri nets was extended with Asynchronous-Channels (ACs) and Time-Domains (TDs) to support Globally-Asynchronous Locally-Synchronous (GALS) systems’ modeling, analysis and implementation. This non-autonomous class of Petri nets is targeted to support the development of automation and embedded systems using a model-based development approach. It benefits from a tool chain framework previously developed, covering the whole development flow, from specification to hardware and software deployment. With the extended Petri net class is possible to model GALS systems, and use the specification to generate the corresponding state space supporting the behavior verification and providing valuable information for implementation.

Verification of petri nets with read arcs

Abstract: Recent work studied the unfolding construction for contextual nets, i.e. nets with read arcs. Such unfoldings are more concise and can usually be constructed more efficiently than for Petri nets. However, concrete verification algorithms exploiting these advantages were lacking so far. We address this question and propose SAT-based verification algorithms for deadlock and reachability of contextual nets. Moreover, we study optimizations of the SAT encoding and report on experiments.