Showing papers on "Petri net published in 1999"

Introduction to Discrete Event Systems

Abstract: Introduction to Discrete Event Systems is a comprehensive introduction to the field of discrete event systems, offering a breadth of coverage that makes the material accessible to readers of varied backgrounds. The book emphasizes a unified modeling framework that transcends specific application areas, linking the following topics in a coherent manner: language and automata theory, supervisory control, Petri net theory, Markov chains and queuing theory, discrete-event simulation, and concurrent estimation techniques. This edition includes recent research results pertaining to the diagnosis of discrete event systems, decentralized supervisory control, and interval-based timed automata and hybrid automata models.

Formalization and verification of event-driven process chains

Abstract: For many companies, business processes have become the focal point of attention. As a result, many tools have been developed for business process engineering and the actual deployment of business processes. Typical examples of these tools are Business Process Reengineering (BPR) tools, Enterprise Resource Planning (ERP) systems, and Workflow Management (WFM) systems. Some of the leading products, e.g. SAP R/3 (ERP/WFM) and ARIS (BPR), use Event-driven Process Chains (EPCs) to model business processes. Although the EPCs have become a widespread process modeling technique, they suffer from a serious drawback: neither the syntax nor the semantics of an EPC are well defined. In this paper, this problem is tackled by mapping EPCs (without connectors of type ∨) onto Petri nets. The Petri nets have formal semantics and provide an abundance of analysis techniques. As a result, the approach presented in this paper gives formal semantics to EPCs. Moreover, many analysis techniques are available for EPCs. To illustrate the approach, it is shown that the correctness of an EPC can be checked in polynomial time by using Petri-net-based analysis techniques.

Modeling, Simulation, and Control of Flexible Manufacturing Systems: A Petri Net Approach

Abstract: Flexible manufacturing systems - an overview Petri nets as an integrated tool and methodology in FMS design fundamentals of Petri nets modelling FMS with Petri nets FMS performance analysis Petri net simulation and tools performance evaluation of pull and push paradigms in flexible automation augmented-timed Petri nets for modelling breakdown handling real-time Petri nets for discrete event control comparison of real-time Petri nets and ladder logic diagrams an object-oriented design methodology for development of FMS control software scheduling using Petri nets Petri nets and future research.

Hybrid Petri net representation of gene regulatory network.

Abstract: It is important to provide a representation method of gene regulatory networks which realizes the intuitions of biologists while keeping the universality in its computational ability. In this paper, we propose a method to exploit hybrid Petri net (HPN) for representing gene regulatory networks. The HPN is an extension of Petri nets which have been used to represent many kinds of systems including stochastic ones in the field of computer sciences and engineerings. Since the HPN has continuous and discrete elements, it can easily handle biological factors such as protein and mRNA concentrations. We demonstrate that, by using HPNs, it is possible to translate biological facts into HPNs in a natural manner. It should be also emphasized that a hierarchical approach is taken for our construction of the genetic switch mechanism of lambda phage which is realized by using HPNs. This hierarchical approach with HPNs makes easier the arrangement of the components in the gene regulatory network based on the biological facts and provides us a prospective view of the network. We also show some computational results of the protein dynamics of the lambda phage mechanism that is simulated and observed by implementing the HPN on a currently available tool.

Interorganizational workflows: An approach based on message sequence charts and petri nets

Abstract: To date, workflow management focuses on improving the effectivity and efficiency of business processes within one organization. However, today’s corporations are challenged to cross organizational boundaries. Phenomena such as electronic commerce, extended enterprises and the Internet stimulate the cooperation between organizations. Therefore, it is interesting to consider workflows distributed over a number of organizations. Interorganizational workflow offers companies the opportunity to re-shape business processes beyond the boundaries of individual organizations. In this paper, we use message sequence charts to specify the interaction between organizations. Petri nets are used to model the workflows inside each organization. Two challenging problems related to interorganizational workflow are tackled in this paper: (1) What are the minimal requirements any interorganizational workflow should satisfy?, and (2) How to decide whether an interorganizational workflow (modeled in terms of Petri nets) is consistent with the interaction structure specified in terms of a message sequence chart?

Telephony call-center scripting by petri net principles and techniques

Abstract: A call center management system comprises a graphical user interface (GUI) adapted for modeling call center behavior, and the behavior of objects within a call center, as Petri Net directed graphs. Once developed, the Petri Net graphs can be compiled as software modules for use in CTI management of a call center. In another aspect the composed Petri Nets are assembled into high-level Petri Nets, and a Petri Net engine is employed to manage a call center. Management techniques and concepts taught are extended to network management as well.

Necessary and sufficient conditions for deadlock-free operation in flexible manufacturing systems using a colored Petri net model

Abstract: Concurrent competition for finite resources by multiple parts in flexible manufacturing systems (FMS) results in deadlock. This is an important issue to be addressed in the operation of the system. A Petri net model, called colored resource-oriented Petri net (CROPN), is developed in this paper. The concurrent resource contention and the important characteristics of the production processes necessary for deadlock control are well modeled by this model. Based on the developed model, necessary and sufficient conditions and an efficient control law are presented for deadlock-free operation in FMS. This control law is a policy of dynamic resource allocation. It determines when a resource can be allocated to which job to avoid deadlock. This control law allows as many active parts as possible to be in the system, while deadlock is totally avoided. This control law is easy to implement and can be embedded into the real-time scheduler. A simple example is used to illustrate the application of the approach.

Efficient Reachability Set Generation and Storage Using Decision Diagrams

Abstract: We present a new technique for the generation and storage of the reachability set of a Petri net Our approach is inspired by previous work on Binary and Multi-valued Decision Diagrams but exploits a concept of locality for the effect of a transition's firing to vastly improve algorithmic performance The result is a data structure and a set of manipulation routines that can be used to generate and store enormous sets extremely efficiently in terms of both memory and execution time

Modeling and analysis of timed Petri nets using heaps of pieces

Abstract: The authors show that safe timed Petri nets can be represented by special automata over the (max, +) semiring, which compute the height of heaps of pieces. This extends to the timed case the classical representation a la Mazurkiewicz of the behavior of safe Petri nets by trace monoids and trace languages. For a subclass including all safe free-choice Petri nets, we obtain reduced heap realizations using structural properties of the net (covering by safe state machine components). The authors illustrate the heap-based modeling by the typical case of safe jobshops. For a periodic schedule, the authors obtain a heap-based throughput formula, which is simpler to compute than its traditional timed event graph version, particularly if one is interested in the successive evaluation of a large number of possible schedules.

Difference Decision Diagrams

Abstract: This paper describes a newdata structure, difference decision diagrams (DDDs), for representing a Boolean logic over inequalities of the form x-y ≤ c where the variables are integer or real-valued.We give algorithms for manipulating DDDs and for determining validity, satisfiability, and equivalence. DDDs enable an efficient verification of timed systems modeled as, for example, timed automata or timed Petri nets, since both the states and their associated timing information are represented symbolically, similar to how BDDs represent Boolean predicates. We demonstrate the efficiency of DDDs by analyzing a timed system and compare the results with the tools KRONOS and UPPAAL.

A framework for scheduler synthesis

Abstract: We present a framework integrating specification and scheduler generation for real time systems. In a first step, the system, which can include arbitrarily designed tasks (cyclic or sporadic, with or without precedence constraints, any number of resources and CPUs) is specified as a timed Petri net. In a second step, our tool generates the most general non preemptive online scheduler for the specification, using a controller synthesis technique.

Dynamic Routing and Operational Controls in Workflow Management Systems

Abstract: Businesses around the world are paying more attention to process management and process automation to improve organizational efficiency and effectiveness. In this paper, we describe a general framework for implementing dynamic routing and operational control mechanisms in Workflow Management Systems (WMSs). The framework consists of three techniques: workflow control tables, sequence constraints, and event-based workflow management rules. Our approach offers several unique features that are missing in commercial workflow management systems: (1) it provides more flexibility in process modeling and control; (2) it permits rework on an ad hoc basis; (3) it handles exceptions to routing and operational controls; and (4) it exploits parallelism to increase system throughput and response time. Finally, the workflow management techniques are applied to the case of consumer loan management and compared with other approaches based on static routing.

Modeling agent conversations with colored petri nets

Abstract: Conversations are a useful means of structuring communica- tive interactions among agents. The value of a conversation- based approach is largely determined by the conversational model it uses. Finite State Machines, used heavily to date for this purpose, are not sucient for complex agent inter- actions requiring a notion of concurrency. We propose the use of Colored Petri Nets as a model underlying a language for conversation speci cation. This carries the relative sim- plicity and graphical representation of the former approach, along with greater expressive power and support for con- currency. The construction of such a language, Protolin- gua, is currently being investigated within the framework of the Jackal agent development environment. In this paper, we explore the use of Colored Petri Nets in modeling agent communicative interaction

Synthesis of embedded software using free-choice Petri nets

Abstract: Software synthesis from a concurrent functional specification is a key problem in the design of embedded systems. A concurrent specification is well-suited for medium-grained partitioning. However, in order to be implemented in software, concurrent tasks need to be scheduled on a shared resource (the processor). The choice of the scheduling policy mainly depends on the specification of the system. For pure dataflow specifications, it is possible to apply a fully static scheduling technique, while for algorithms containing data-dependent control structures, like the if-then-else or while-do constructs, the dynamic behaviour of the system cannot be completely predicted at compile time and some scheduling decisions are to be made at run-time. For such applications we propose a Quasi-Static Scheduling (QSS) algorithm that generates a schedule in which run-time decisions are made only for data-dependent control structures. We use Free Choice Petri Nets (FCPNs), as the underlying model, and define quasi-static schedulability for FCPNs. The proposed algorithm is complete, in that it can solve QSS for any FCPN that is quasi-statically schedulable. Finally, we show how to synthesize from a quasi-static schedule a C code implementation that consists of a set of concurrent tasks.

Monitoring Discrete Event Systems Using Petri Net Embeddings

Abstract: In this paper we discuss a methodology for monitoring failures and other activity in discrete event systems that are described by Petri nets Our method is based on embedding the given Petri net model in a larger Petri net that retains the functionality and properties of the given one, perhaps in a non-separate (that is, not immediately identifiable) way This redundant Petri net embedding introduces "structured redundancy" that can be used to facilitate fault detection, identification and correction, or to offer increased capabilities for monitoring and control We focus primarily on separate embeddings in which the functionality of the original Petri net is retained in its exact form Using these embeddings, we construct monitors that operate concurrently with the original system and allow us to detect and identify different types of failures by performing consistency checks between the state of the original Petri net and that of the monitor The methods that we propose are attractive because the resulting monitors are robust to failures, they may not require explicit acknowledgments from each activity, and their construction is systematic and easily adaptable to restrictions in the available information We also discuss briefly how to construct nonseparate Petri net embeddings

Network Algebra

Abstract: From the Publisher: Network Algebra considers the algebraic study of networks and their behaviour. It contains general results on the algebraic theory of networks, recent results on the algebraic theory of models for parallel programs, as well as results on the algebraic theory of classical control structures. The results are presented in a unified framework of the calculus of flownomials, leading to a sound understanding of the algebraic fundamentals of the network theory." "The term 'network' is used in a broad sense within this book, as consisting of a collection of interconnecting cells, and two radically different specific interpretations of this notion of networks are studied. One interpretation is additive, when only one cell is active at a given time - this covers the classical models of control specified by finite automata or flowchart schemes. The second interpretation is multiplicative, where each cell is always active, covering models for parallel computation such as Petri nets or dataflow networks. More advanced settings, mixing the two interpretations are included as well." "Network Algebra will be of interest to anyone interested in network theory or its applications and provides them with the results needed to put their work on a firm basis. Graduate students will also find the material within this book useful for their studies.

ERCN-merged nets and their analysis using siphons

Abstract: This paper generalizes the modular approach proposed by Jeng and DiCesare (1995) for modeling manufacturing systems with shared resources. First, the-dynamic behavior of each resource is modeled separately using extended resource control nets (ERCNs). An important feature of ERCNs is their capability to express explicitly assembly operations and parallel processes, which is not possible with resource control nets. Interactions among the resources are then modeled through merging of common transitions and common transition subnets. This paper provides conditions, expressed in terms of siphons, under which reversibility and liveness of the integrated model are obtained. Relations between siphons, circular structure and circular-wait are formally established.

Woflan: a Petri-net-based workflow analyzer

Abstract: Workflow management promises a new solution to an age-old problem: controlling, monitoring, optimizing and supporting business processes. What is new about workflow management is the explicit representation of the business process logic which allows for computerized support. Unfortunately, today’s systems give hardly any support to verify the correctness of workflow processes. This paper discusses a verification tool Woflan. Woflan uses state-of-the-art results from Petri net theory, and interfaces with some of the leading workflow tools at the Dutch market. This paper describes the architecture of Woflan and illustrates its functionality by means of some small examples.

Component-based software architectures : a framework based on inheritance of behavior

Abstract: Software architectures shift the focus of developers from lines-ofcode to coarser-grained components and their interconnected structure. Unlike fine-grained objects, these components typically encompass business functionality and need to be aware of the underlying business processes. Hence, the interface of a component should refiect relevant parts of the business process and the software architecture should emphasize the coordination among components. To shed light on these issues, we provide a framework for component-based software architectures focussing on the process perspective. The interface of a component is described in terms of Petri nets and projection inheritance is used to determine whether a component "fits". Compositionality and substitutability are key issues for component-based development. This paper provides new results to effectively deal with these issues.

On non-decidability of reachability for timed-arc Petri nets

Abstract: Timed-arc Petri nets are not Turing powerful, because, in particular, they cannot simulate a counter with test on zero. Thus, we could think that this model does not extend significantly the expressiveness of untimed Petri nets. But this is not true; in this paper we show that the differences between them are big enough to make the reachability problem undecidable. We also define dead tokens as those that cannot be used for firing any transitions in the future and we present some particular cases where we can identify them on this kind of timed nets.

An Unfolding Algorithm for Synchronous Products of Transition Systems

Abstract: The unfolding method, initially introduced for systems modelled by Petri nets, is applied to synchronous products of transition systems, a model introduced by Arnold [2]. An unfolding procedure is provided which exploits the product structure of the model. Its performance is evaluated on a set of benchmarks.

Discrete-event simulation of fluid stochastic Petri nets

Abstract: The purpose of this paper is to describe a method for the simulation of the recently introduced fluid stochastic Petri nets. Since such nets result in rather complex system of partial differential equations, numerical solution becomes a formidable task. Because of a mixed (discrete and continuous) state space, simulative solution also poses some interesting challenges, which are addressed in the paper.

Possibilistic Petri nets

Abstract: This paper presents the possibilistic Petri net model which combines possibility logic with Petri nets with objects. The main feature of this model is to allow one to reason about the aspects of uncertainty and change in dynamic discrete event systems. The paper presents relevant concepts of Petri nets with objects and possibility logic and how imprecision and vagueness are introduced in the marking of a Petri net with objects. The marking of a net is imprecise, or in a more general way, fuzzy, in order to represent an ill-known knowledge about a system state. A new marking updating according to the fuzzy marking such defined is also discussed. An example of shop door monitoring is presented that illustrates our approach.

FunState—an internal design representation for codesign

Abstract: In this paper, an internal design model called FunState (functions driven by state machines) is presented that enables the representation of different types of system components and scheduling mechanisms using a mixture of functional programming and state machines.It is shown here how properties relevant for scheduling and verification of specification models like boolcan dataflow, cyclostatic dataflow, synchronous dataflow, marked graphs, and communicating state machines as well as Petri nets may be represented in the FunState model. Examples of methods suited for FunState are described, such as scheduling and verification. They are based on the representation of the model's state transitions in form of a periodic graph.

Using logic programs with stable model semantics to solve deadlock and reachability problems for 1-safe petri nets

Abstract: McMillan has presented a deadlock detection method for Petri nets based on finite complete prefixes (i.e. net unfoldings). The approach transforms the PSPACE-complete deadlock detection problem for a 1-safe Petri net into a potentially exponentially larger NP-complete problem of deadlock detection for a finite complete prefix. McMillan devised a branch-and-bound algorithm for deadlock detection in prefixes. Recently, Melzer and Romer have presented another approach, which is based on solving mixed integer programming problems. In this work it is shown that instead of using mixed integer programming, a constraint-based logic programming framework can be employed, and a linear-size translation from deadlock detection in prefixes into the problem of finding a stable model of a logic program is presented. As a side result also such a translation for solving the reachability problem is devised. Correctness proofs of both the translations are presented. Experimental results are given from an implementation combining the prefix generator of the PEP-tool, the translation, and an implementation of a constraint-based logic programming framework, the smodels system. The experiments show the proposed approach to be quite competitive, when compared to the approaches of McMillan and Melzer/Romer.

Modeling, Verification and Exploration of Task-Level Concurrency in Real-Time Embedded Systems

Abstract: From the Publisher: The combination of VLSI process technology and real-time digital signal processing (DSP) has brought a break-through in information technology. This rapid technical (r)evolution allows the integration of ever more complex systems on a single chip. However, these technology and integration advances have not been matched by an increase in design productivity, causing technology to leapfrog the design of integrated circuits (ICs). The success of these emerging `systems-on-a-chip' (SOC) can only be guaranteed by a systematic and formal design methodology, possibly automated in computer-aided design (CAD) tools, and effective re-use of existing intellectual property (IP). In this book, a contribution is made to the modeling, timing verification and analysis, and the automatic synthesis of integrated real-time DSP systems. Existing literature in these three domains is extensively reviewed, making this book the first to give a comprehensive overview of existing techniques. The emphasis throughout the book is on the support and guaranteeing of the real-time aspect and constraints of these systems, which avoids time consuming design iterations and safeguards the ever shrinking time-to-market. The proposed `Multi-Thread Graph' (MTG) system model features two-layers, unifying a (timed) Petri net and a control-data flow graph. Its unique interface between both models offers the best of two worlds and introduces an extra abstraction level hiding the operation-level details which are unnecessary during global system exploration. The formulated timing analysis and verification approach supports the calculation of temporal separation between different MTG entities as well as realisticperformance metrics for highly concurrent systems. The synthesis methodology focuses on managing the task-level concurrency (i.e. task scheduling), as part of a proposed overall system design meta flow. It emphasizes performance and timing aspects (`timeliness'), while minimizing processor cost overhead as driven by high-level cost estimators. The approach is new in the abstraction level it employs, and in its optimal hybrid dynamic/static scheduling policy which, driven by cost estimators, selects the scheduling policy for each behavior. At the low-level, RTOS synthesis generates an application-specific scheduler for the software component. The proposed synthesis methodology (at the task-level) is asserted to yield most optimal results when employed before the hardware/software partition is made. At this level, the distinction between these two is minimal, such that all steps in the design trajectory can be shared, thereby reducing the system cost significantly and allowing tighter satisfaction of timing/performance constraints.