Showing papers on "Process architecture published in 1997"

Verification of Workflow Nets

Abstract: Workflow management systems will change the architecture of future information systems dramatically. The explicit representation of business procedures is one of the main issues when introducing a workflow management system. In this paper we focus on a class of Petri nets suitable for the representation, validation and verification of these procedures. We will show that the correctness of a procedure represented by such a Petri net can be verified by using standard Petri-net-based techniques. Based on this result we provide a comprehensive set of transformation rules which can be used to construct and modify correct procedures.

Deadlock analysis of Petri nets using siphons and mathematical programming

Abstract: This paper exploits the potential of siphons for the analysis of Petri nets, It generalizes the well-known Commoner condition and is based on the notion of potential deadlocks which are siphons that eventually become empty. A linear programming based sufficient condition under which a siphon is not a potential deadlock is obtained. Based on the new sufficient condition, a mathematical programming approach and a mixed-integer programming approach are proposed for checking general Petri nets and structurally bounded Petri nets respectively without explicitly generating siphons. Stronger results are obtained for asymmetric choice nets and augmented marked graphs. In particular, we show that an asymmetric choice net is live iff it is potential-deadlock-free and an augmented marked graph is live and reversible iff it is potential-deadlock-free.

A Survey of Petri Net Methods for Controlled Discrete EventSystems

Abstract: This paper surveys recent research on the application of Petri net models to the analysis and synthesis of controllers for discrete event systems. Petri nets have been used extensively in applications such as automated manufacturing, and there exists a large body of tools for qualitative and quantitative analysis of Petri nets. The goal of Petri net research in discrete event systems is to exploit the structural properties of Petri net models in computationally efficient algorithms for computing controls. We present an overview of the various models and problems formulated in the literature focusing on two particular models, the controlled Petri nets and the labeled nets. We describe two basic approaches for controller synthesis, based on state feedback and event feedback. We also discuss two efficient techniques for the on-line computation of the control law, namely the linear integer programming approach which takes advantage of the linear structure of the Petri net state transition equation, and path-based algorithms which take advantage of the graphical structure of Petri net models. Extensions to timed models are briefly described. The paper concludes with a discussion of directions for future research.

Petri Nets, Commutative Context-Free Grammars, and Basic Parallel Processes

Abstract: The paper provides a structural characterisation of the reachable markings of Petri nets in which every transition has exactly one input place. As a corollary, the reachability problem for this class is proved to be NP-complete. Further consequences are: the uniform word problem for commutative context-free grammars is NP-complete; weak-bisimilarity is semidecidable for Basic Parallel Processes.

A Brief Introduction to Coloured Petri Nets

Abstract: Coloured Petri Nets (CP-nets or CPN) is a graphical oriented language for design, specification, simulation and verification of systems. It is in particular well-suited for systems in which communication, synchronisation and resource sharing are important. Typical examples of application areas are communication protocols, distributed systems, imbedded systems, automated production systems, work flow analysis and VLSI chips.

Choice-free Petri nets: a model for deterministic concurrent systems with bulk services and arrivals

Abstract: Among discrete event systems, those exhibiting concurrency are especially challenging, requiring the use of formal methods to deal with them. Petri nets are a well-established such formalism. The structure theory aims at overcoming the state space explosion problem, inherent to the analysis of concurrent systems, by bridging structural and behavioral properties. To date, this has been successfully achieved mainly for some subclasses of ordinary nets. However weights are a modeling convenience in many situations. In this paper we study a formal model for a subclass of concurrent systems with bulk services and arrivals which structurally avoids conflicts. Structural results and techniques for dealing with them are introduced. These include structural conditions on properties of correct behavior and a unified framework for checking general behavioral properties by reasoning solely on the structure.

Discrete-event simulation of fluid stochastic Petri nets

Abstract: The purpose of the paper is to describe a method for the simulation of recently introduced fluid stochastic Petri nets. Since such nets result in a rather complex set 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.

A Petri net approach to fault detection and diagnosis in distributed systems. I. Application to telecommunication networks, motivations, and modelling

Abstract: This paper presents a new use of safe Petri nets in the field of distributed discrete event systems, with application to telecommunication network management. This study has in its long range objectives to provide a generic supervisor, which can be easily distributed on a set of sensors. Petri nets are used to provide both a model and an algorithm in fault management domain. Key features of our approach are (1) we take advantage of the ability of Petri Nets to model concurrency in distributed systems, (2) we refuse using the marking graph in our algorithms in order to avoid state explosion and thus rely instead in the so-called partial order semantics of Petri nets, and (3) our algorithms use net unfolding techniques and extend them to the probabilistic case by providing a generalized Viterbi algorithm. This paper concentrates on application, motivations, and modelling.

Time Processes for Time Petri-Nets

Abstract: The objective of this work is to give Merlin's time Petri nets a partial order semantics based on the nonsequential process semantics for untimed net systems.

Efficiency of Asynchronous Systems and Read Arcs in Petri Nets

Abstract: Two solutions to the MUTEX-problem are compared w.r.t. their temporal efficiency. For this, a formerly developed efficiency-testing for asynchronous systems is adapted to nets with so-called read arcs. The close relation between efficiency-testing and fairness is pointed out, and it is shown that read arcs are necessary for any solution to the MUTEX-problem.

Petri nets for simulation and modeling of construction systems

Abstract: For the past 20 years, investigators have studied the simulation and modeling of construction systems. The authors of this paper introduce Petri nets--a powerful modeling tool used previously for modeling computer networks and automated manufacturing systems--that can successfully model construction systems. This paper describes the Petri net technique for modeling and illustrates how models of construction systems can be devised. Several common Petri net structures are described, along with features that are useful in construction system modeling. Time and color Petri nets and their application in modeling specific characteristics of construction systems are discussed. Two examples are provided that illustrate the advantages and disadvantages of Petri nets as tools for the modeling and simulation of construction operations.

An extended Petri net model for supporting workflow in a multilevel secure environment

Abstract: This paper makes three contributions to the area of multilevel secure (MLS) workflow management systems (WFMS). First, it proposes a multilevel secure workflow transaction model. This model identifies the task dependencies in a workflow that cannot be enforced in order to meet multilevel security constraints. Second, it shows how Petri nets, a mathematical as well as a graphical tool, can be used to represent various types of task dependencies. Third, it extends the original Petri net (PN) model by proposing a Secure Petri Net (SPN) that can automatically detect and prevent all the task dependencies that violate security. This paper then presents algorithms to construct and execute MLS workflow transactions.

A class of Petri nets for manufacturing system integration

Abstract: This paper introduces a class of Petri nets which are reversible, live, and can be kept bounded. Furthermore, these Petri nets have output transitions that can be fired independently from each other. These properties are required when modeling manufacturing systems. Another important property is that the integration of models which belong to this class of Petri nets still belongs to the same class, assuming that the integration is performed following rules which reflect common manufacturing practice. As a result, the qualitative properties of the module models are preserved. The results obtained in this paper are expected to shed light on the design, management and control of large scale manufacturing systems since modular approach is a way to cope with complexity.

Modeling of hybrid systems using continuous and hybrid Petri nets

Abstract: We shall first try to define what is meant by a hybrid system. Petri nets are, by definition, discrete event systems. However, continuous Petri nets have subsequently been defined. Both models can be combined to produce what are known as hybrid Petri nets. These continuous and hybrid nets are used to model hybrid systems whether or not time is taken into account. These models are explained intuitively, and applications are described.

Minimal Transition Systems for History-Preserving Bisimulation

Abstract: In this paper we propose a new approach to check history-preserving equivalence for Petri nets Exploiting this approach, history-preserving bisimulation is proved decidable for the class of finite nets which are n-safe for some n (the approaches of [17] and of [8] work just for 1-safe nets) Moreover, since we map nets on ordinary transition systems, standard results and algorithms can be re-used, yielding for instance the possibility of deriving minimal realizations The proposed approach can be applied also to other concurrent formalisms based on partial order semantics, like CCS with causality [4]

Modeling interactive systems with hierarchical colored petri nets

Abstract: This paper addresses the problem of modeling interactive systems * . We aim to provide an easy way for elaborating the behavior specification of a system using hierarchical colored Petri nets. Our modeling approach comprises two levels of

Petri nets for modeling automated manufacturing systems with error recovery

Abstract: This paper enhances a Petri net synthesis theory with the capability to deal with reversibility, which is an important property related to the concept of error recovery in manufacturing. The theory has been proposed to synthesize a class of Petri nets for modeling shared-resource automated manufacturing systems. The class of nets has been shown to be conservative (bounded) and possess structural liveness under two sufficient conditions. The conditions can be checked structurally by an algorithm without enumerating the states. A bounded and live net means that the modeled system cannot have capacity overflows and deadlocks, two types of unwanted behaviors in manufacturing. In this paper it is further proven that under these two sufficient conditions, the class of nets possesses reversibility. Thus the liveness-checking algorithm can be used to check reversibility without modification.

Designing a re‐engineering proof process architecture

Abstract: Argues that it can be very difficult for someone coming to an organization, with the job of designing or modelling some or all of its processes, to know how to cut the mass of organizational activity up into component processes and to see how they are related; in other words, to determine the process architecture of the organization. Calls for a partitioning into processes, that as far as possible, completely aligned to the business in which the organization is in and as independent as possible of how the business chooses to organize itself. Describes an approach to solving the problem.

PNtalk - a Computerized Tool for Object Oriented Petri Nets Modelling

Abstract: The paper deals with a new formalism and a tool for concurrent systems modelling and prototyping. This formalism, Object Oriented Petri Net (OOPN), combines the descriptive power of Petri nets with the well known advantages of object oriented modelling techniques. In the paper there are presented the structure of system specifications by means of OOPNs, principles of their dynamic behaviour as well as some basic features of a computerized tool which supports practical use of OOPNs. This tool works with a language called PNtalk which is based on the OOPNs and the language Smalltalk.

Time constraint verification methods based on time Petri nets

Abstract: The study is concerned with the development of real time distributed applications and more precisely with the verification of temporal properties in a distributed context (taking into account the characteristics of the real architecture). We show how to use a time Petri net based model of the application in order to prove that a communication system (networks, protocols) and a mapping of tasks meet specified temporal properties.

Analysis of Petri Nets with a Dynamic Priority Method

Abstract: In this paper we propose an efficient reachability set based Petri net analysis by introducing dynamic priorities which decreases the number of reachable markings in most cases. It is proved that for specific dynamic priority relations certain properties (especially liveness and the existence of home states) do hold if and only if these properties do also hold for the Petri net without priorities. We present an algorithm based on these priority relations additionally exploiting T-invariants thus being able to benefit from the structure of the net.

Behavioral Petri nets: a model for diagnostic knowledge representation and reasoning

Abstract: Some of the most popular approaches to model-based diagnosis consist of reasoning about a model of the behaviour of the system to be diagnosed by considering a set of observations about such a system and by explaining it in terms of a set of initial causes. This process has been widely modeled via logical formalisms essentially taking into account declarative aspects. In this paper, a new approach is proposed, where the diagnostic process is captured within a framework based on the formalism of Petri nets. We introduce a particular net model, called Behavioral Petri Net (BPN), We show how the formalization of the diagnostic process can be obtained in terms of reachability in a BPN and can be implemented by exploiting classical analysis techniques of Petri nets like reachability graph analysis and P-invariant computation. Advantages of the proposed methods, like suitability to parallel processing and exploitation of linear algebra techniques, are then pointed out.

Hierarchical time-extended Petri nets as a generic tool for power system restoration

Abstract: Power system restoration following a system collapse, is a very complex task. A wide variety of control actions has to be performed on time, while constraints such as power balance and system stability have to be carefully respected. In this paper, hierarchical time-extended Petri nets are exploited, in order to support the restoration process. The proposed framework has been applied to the blackstart of the Hellenic power system. Crucial issues pertaining to the restoration procedures are identified and the corresponding Petri net models are presented.