Showing papers on "Process architecture published in 2002"
TL;DR: This paper integrates several important characteristics of PD processes into a single model, highlighting the effects of varying process architecture and yielding several managerial insights, including: how rework cascades through a PD process, trading off cost and schedule risk, interface criticality, and occasions for iterative overlapping.
Abstract: To gain competitive leverage, firms that design and develop complex products seek to increase the efficiency and predictability of their development processes. Process improvement is facilitated by the development and use of models that account for and illuminate important characteristics of the process. Iteration is a fundamental but often unaddressed feature of product development (PD) processes. Its impact is mediated by the architecture of a process, i.e., its constituent activities and their interactions. This paper integrates several important characteristics of PD processes into a single model, highlighting the effects of varying process architecture. The PD process is modeled as a network of activities that exchange deliverables. Each activity has an uncertain duration and cost, an improvement curve, and risks of rework based on changes in its inputs. A work policy governs the timing of activity execution and deliverable exchange (and thus the amount of activity concurrency). The model is analyzed via simulation, which outputs sample cost and schedule outcome distributions. Varying the process architecture input varies the output distributions. Each distribution is used with a target and an impact function to determine a risk factor. Alternative process architectures are compared, revealing opportunities to trade cost and schedule risk. Example results and applications are shown for an industrial process, the preliminary design of an uninhabited combat aerial vehicle. The model yields and reinforces several managerial insights, including: how rework cascades through a PD process, trading off cost and schedule risk, interface criticality, and occasions for iterative overlapping.
502 citations
Book•
IBM1
TL;DR: This book presents an introduction to Stochastic Petri Nets covering the modeling power of the proposed SPN model, the stability conditions and the simulation methods.
Abstract: Written by a leading researcher this book presents an introduction to Stochastic Petri Nets covering the modeling power of the proposed SPN model, the stability conditions and the simulation methods. Its unique and well-written approach provides a timely and important addition to the literature. Appeals to a wide range of researchers in engineering, computer science, mathematics and OR.
228 citations
Book•
01 Jan 2002
TL;DR: In this book abstraction is used to create larger nets from smaller ones, and this kind of abstraction will be represented graphically as shown in Figure 2.13c.
Abstract: ion, however, has a meaningful interpretation. To give an example, consider the fragment of a net in Figure 2.13a. Intuitively the abstraction in 2.4 Refinement and Composition 21 Figure 2.13d has a corresponding behaviour ("a token is passed through"). Figure 2.13d is also an abstraction of Figure 2.13b, but now the behaviour is different. In Figure 2.13d a token can pass, but not so in Figure 2.13b. Note that the set Y to be abstracted is not necessarily connected as a subgraph. However, Figure 2.13d can be interpreted as a merge of two places. This operation is called a fusion of places or place fusion. It will be used in Part II of this book to create larger nets from smaller ones. This kind of abstraction will be represented graphically as shown in Figure 2.13c. The dual situation for a transition-bordered set is shown in Figures 2.13e-h. Thus Figures 2.13f, g and h describe a fusion of transitions or transition fusion. -1 -I
186 citations
17 Jan 2002
TL;DR: The paper introduces the basic motivations for modelling DEDS and briefly overviews the basic results of net theory that are useful for the definition of Stochastic Petri Nets and Generalized Stochastics Nets and GSPNs.
Abstract: Stochastic Petri Nets are a modelling formalism that can be conveniently used for the analysis of complex models of Discrete Event Dynami Systems (DEDS) and for their performance and reliability evaluation. The automatic construction of the probabilistic models that underly the dynamic behaviours of these nets rely on a set of results that derive from the theory of untimed Petri nets. The paper introduces the basic motivations for modelling DEDS and briefly overviews the basic results of net theory that are useful for the definition of Stochastic Petri Nets and Generalized Stochastic Petri Nets. The different approaches that have been used for introducing the concept of time in these models are discussed in order to provide the basis for the definition of SPNs and GSPNs as well. Details on the solution techniques and on their computational aspects are provided. A brief overview of more advanced material is included at the end of the paper to highlight the state of the art in this field and to give pointers to relevant results published in the literature.
170 citations
10 Dec 2002
TL;DR: The paper presents an extension of the classical Banker's algorithm to a class of flexible manufacturing systems modeled by means of Petri nets, which have two interesting characteristics from the application point of view.
Abstract: Banker's-like approaches to deadlock avoidance are based on a decision procedure to grant active processes resources using information about the maximum needs of resources that a process can request in order to ensure termination. The paper presents an extension of the classical Banker's algorithm to a class of flexible manufacturing systems modeled by means of Petri nets. These systems have two interesting characteristics from the application point of view. First, flexible routing of parts is allowed, and second, a multiset of resources is allowed to be used at each processing step. The decision procedure introduced is polynomial in the Petri net model size.
135 citations
TL;DR: In this paper, recent research on Petri net applications in batch processes is presented, and future directions are discussed.
79 citations
15 Jul 2002
TL;DR: Reference nets are a well-established means for the description of concurrent systems as discussed by the authors, which can be used to design executable multi-agent systems while hiding the sometimes annoying details of concurrent implementations in traditional programming languages.
Abstract: A multi-agent system has a high degree of concurrency. Petri nets are a well-established means for the description of concurrent systems. Reference nets are higher level, object-oriented Petri nets. With Renew (REference NEt Workshop), there exists a tool to model and execute reference nets with seamless Java integration. So, reference nets can be used to design executable multi-agent systems while hiding the sometimes annoying details of concurrent implementations in traditional programming languages. The technique is currently used to implement a FIPA-compliant agent platform for multi-agent systems (called CAPA) focused on retaining a maximum level of concurrency in the system.
75 citations
01 Jan 2002
TL;DR: Cyclic Communicating Processes: A Logical View and Is the Die Cast for the Token Game?
Abstract: Cyclic Communicating Processes: A Logical View . . . . . . . . . . . . . . . . .68 P. S. Thiagarajan Is the Die Cast for the Token Game? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 Alex Yakovlev
64 citations
TL;DR: It is shown that the general Petri net synthesis problem and its distributed version may both be solved in time polynomial in the size of the given graph.
Abstract: The synthesis problem for Petri nets consists in deciding constructively the existence of a Petri net with sequential state graph isomorphic to a given graph. If events are attached to locations, one may set as an additional requirement that the synthesised net should be distributable; i.e. such that events at different locations have no common input place, whence distributed conflicts are avoided. Distributable nets are easily implemented by finite families of automata (one per location) communicating with each other by asynchronous message passing. We show that the general Petri net synthesis problem and its distributed version may both be solved in time polynomial in the size of the given graph. We report on some preliminary experiments of Petri net synthesis applied to the distribution of reactive automata using the tool SYNET.
64 citations
TL;DR: It has been shown experimentally that the developed siphon truncation technique enhances the ability to develop deadlock-free schedules of systems with a high number of deadlocks, which cannot be achieved using standard Petri net scheduling approaches.
Abstract: This paper addresses the deadlock-free scheduling problem in Flexible Manufacturing Systems. An efficient deadlock-free scheduling algorithm was developed, using timed Petri nets, for a class of FMSs called Systems of Sequential Systems with Shared Resources (S 4 R). The algorithm generates a partial reachability graph to find the optimal or near-optimal deadlock-free schedule in terms of the firing sequence of the transitions of the Petri net model. The objective is to minimize the mean flow time (MFT). An efficient truncation technique, based on the siphon concept, has been developed and used to generate the minimum necessary portion of the reachability graph to be searched. It has been shown experimentally that the developed siphon truncation technique enhances the ability to develop deadlock-free schedules of systems with a high number of deadlocks, which cannot be achieved using standard Petri net scheduling approaches. It may be necessary, in some cases, to relax the optimality condition for large F...
62 citations
TL;DR: An approach to the schedulability analysis of real-time systems modeled in time Petri nets by separating timing properties from other behavioral properties is presented, which not only improves efficiency but also facilitates the discussion of the reachability issue with regard to Schedulability.
Abstract: This paper presents an approach to the schedulability analysis of real-time systems modeled in time Petri nets by separating timing properties from other behavioral properties. The analysis of behavioral properties is conducted based on the reachability graph of the underlying Petri net, whereas timing constraints are checked in terms of absolute and relative firing domains. If a specific task execution is schedulable, we calculate the time span of the task execution, and pinpoint nonschedulable transitions to help adjust timing constraints. A technique for compositional timing analysis is also proposed to deal with complex task sequences, which not only improves efficiency but also facilitates the discussion of the reachability issue with regard to schedulability. We identified a class of well-structured time Petri nets such that their reachability can be easily analyzed.
TL;DR: Overlapping decompositions and expansions are considered to design decentralized controllers for discrete-event systems (DESs) modeled by Petri nets and it is shown that properties like boundedness, reversibility, and liveness carry over from the including net to the included net.
Abstract: Overlapping decompositions and expansions are considered to design decentralized controllers for discrete-event systems (DESs) modeled by Petri nets. The inclusion principle for Petri nets is first defined. It is shown that properties like boundedness, reversibility, and liveness (with a mild additional condition) carry over from the including net to the included net. Moreover, a new property called obstruction, is introduced for the including net, and it is shown that if obstruction does not occur in the including net, then deadlock does not occur in the included net. An expansion procedure, which guarantees inclusion for an overlappingly decomposed Petri net, is then introduced.
11 Oct 2002
TL;DR: Improved facilities for performance analysis using coloured Petri nets are provided, including facilities for collecting data, running multiple simulations, generating statistically reliable simulation output, and comparing alternative system configurations.
Abstract: This paper provides an overview of improved facilities for performance analysis using coloured Petri nets. Coloured Petri nets is a formal method that is well suited for modeling and analyzing large and complex systems. The paper describes steps that have been taken to make a distinction between modeling the behavior of a system and observing the behavior of a model. Performance-related facilities are discussed, including facilities for collecting data, running multiple simulations, generating statistically reliable simulation output, and comparing alternative system configurations.
TL;DR: The incidence matrices—from places to transitions and vice versa—of an acyclic Petri net can obtain a block-triangular structure by reordering their rows and columns, which allows the efficient solution of some reachability problems for acy Cleric Petri nets.
Abstract: The incidence matrices—from places to transitions and vice versa—of an acyclic Petri net can obtain a block-triangular structure by reordering their rows and columns. This allows the efficient solution of some reachability problems for acyclic Petri nets. This result is further used in supervisory control of Petri nets; supervisors for Petri nets with uncontrollable transitions are constructed by extending the method of Yamalidou et al. (1996) to Petri nets where transitions can be executed simultaneously. A large class of Petri nets with uncontrollable transitions is given for which the maximally permissive supervisor can be realized by a Petri net. The original specification is algorithmically transformed—by using the results for acyclic Petri nets—into a new specification to take the presence of uncontrollable transitions into account. The supervisor is obtained by simple matrix multiplications and no linear integer programs need to be solved. Furthermore, a class of Petri nets is given for which the supervisor can be realized by extending the enabling rule with OR-logic.
TL;DR: A tool called C2Petri has been developed which converts C-Pthreads programs to the equivalent Petri net model and helps verification of Pthread-based programs.
Abstract: Since most modern computing systems contain multiple processing elements, applications are relying on multithreaded programming techniques that allow a program to execute multiple tasks concurrently to take advantage of the processing capabilities. Multithreaded programs are more difficult to design and test because of the nondeterministic execution orders and synchronization among the threads. Different approaches can be used to test Multithreaded Applications. In our approach we use Petri nets to represent the key elements of interactions among threads to identify potential problems such as race conditions, lost signals, and deadlocks. A tool called C2Petri has been developed which converts C-Pthreads programs to the equivalent Petri net model. This tool helps verification of Pthread-based programs. At present the tool has limited capabilities and we hope to expand the capabilities of our tool in the near future.
03 Sep 2002
TL;DR: Petri nets are applied to provide a modular representation of urban traffic systems regulated by signalized intersections to describe thoroughly the movement of vehicles in the traffic network via timed Petri nets.
Abstract: Significant classes of transportation systems can be represented by Petri net models. In this paper, Petri nets are applied to provide a modular representation of urban traffic systems regulated by signalized intersections. The basic idea is to consider such systems to be composed of elementary structural components, namely, intersections and road stretches. In order to describe thoroughly the movement of vehicles in the traffic network, a microscopic representation is adopted and realized via timed Petri nets. An interesting feature of the designed model consists in the possibility of representing the offsets among different traffic light cycles as embedded in the structure of the model itself. In turn, that allows us to simply implement the coordination among traffic light timings, which facilitates the description and solution of the relevant optimization problems.
Book•
10 Jan 2002
TL;DR: This paper focuses on improving the Usability of Petri Nets with the Petri Net Baukasten, and implementation of Parameterized Net Classes with thePetri Net Kernel of the Petrinetz-Baukastsen.
Abstract: "What Is a Petri Net?" Informal Answers for the Informed Reader.- Application Oriented Approaches.- The ?Petri Net Baukasten?: An Overview.- Improving the Usability of Petri Nets with the ?Petri Net Baukasten?.- Implementation of Parameterized Net Classes with the Petri Net Kernel of the ?Petrinetz-Baukasten?.- Process Landscaping: Modelling Distributed Processes and Proving Properties of Distributed Process Models.- Unifying Frameworks.- Petri Nets over Partial Algebra.- Parameterized Net Classes: A Uniform Approach to Petri Net Classes.- Behavior and Realization Construction for Petri Nets Based on Free Monoid and Power Set Graphs.- Rewriting Logic as a Unifying Framework for Petri Nets.- Theoretical Approaches.- Generalized Automata and Their Net Representations.- On Concurrent Realization of Reactive Systems and Their Morphisms.- Transactions and Zero-Safe Nets.- Two Algebraic Process Semantics for Contextual Nets.- Continuous Petri Nets and Transition Systems.
07 Jan 2002
TL;DR: This paper presents a Petri net-based generic framework for modeling e-negotiation, and provides a theoretical framework for studying e-Negotiation activities at a conceptual and logical level.
Abstract: Electronic negotiation involves two or more agents multilaterally bargaining for mutual gain, using information technologies in a cooperative problem-solving (CPS) environment. Most of the existing work deals with the development of strategies for supporting negotiation activities in a pre-defined problem structure. In this paper, we focus on the information flow among the different entities of e-negotiation. We present a Petri net-based generic framework for modeling e-negotiation. Our approach provides a theoretical framework for studying e-negotiation activities at a conceptual and logical level.
TL;DR: High-level processes with data type behavior, amalgamation, and other kinds of constructions, which are essential aspects for a proposed component concept for high-level nets are discussed.
Abstract: The notion of processes for low-level Petri nets based on occurrence nets is well known and it represents the basis for the study of the non-sequential behavior of Petri nets. Processes for high-level nets N are often defined as processes of the low level net Flat(N) which is obtained from N via a construction called "flattening". In this paper we define high-level processes for high-level nets based on a suitable notion of high-level occurrence nets. The flattening of a high-level occurrence net is in general not a low-level occurrence net, due to so called "assignment conflicts" in the high-level net. The main technical result is a syntactical characterization of assignment conflicts. But the main focus of this paper is a conceptual discussion of future perspectives of high-level net processes includingc oncurrency and data type aspects. Specifically, in the second part of the paper, we discuss possible extensions of high-level net processes, which are formally introduced for algebraic high-level nets in the first part of this paper. Of special interest are high-level processes with data type behavior, amalgamation, and other kinds of constructions, which are essential aspects for a proposed component concept for high-level nets.
08 May 2002
TL;DR: This work considers the problem of enforcing linear constraints containing marking terms, firing vector terms, and Parikh vector terms and shows how this new type of constraints can be enforced in Petri nets.
Abstract: Considers the problem of enforcing linear constraints containing marking terms, firing vector terms, and Parikh vector terms. Such constraints increase the expressivity power of the linear marking constraints. We show how this new type of constraints can be enforced in Petri nets. In the case of fully controllable and observable Petri nets, we give the construction of a supervisor enforcing such constraints. In the case of Petri nets with uncontrollable and/or unobservable transitions, we reduce the supervisor synthesis problem to enforcing linear marking constraints on a transformed Petri net.
TL;DR: The main result is that it is possible to obtain a framework where process expressions can be given two, entirely consistent, kinds of semantics: one based on Petri nets, the other on SOS rules.
Abstract: The paper describes a Petri net as well as a structural operational semantics for an algebra of process expressions. It specifically addresses this problem for the box algebra, a model of concurrent computation which combines Petri nets and standard process algebras. The main result is that it is possible to obtain a framework where process expressions can be given two, entirely consistent, kinds of semantics: one based on Petri nets, the other on SOS rules. This consistency can also be extended to a partial order semantics.
Proceedings Article•
01 Jun 2002TL;DR: This work explores the usefulness of some higher-order Petri nets techniques by looking at them from an application point of view and by illustrating them with small to medium-sized application examples.
Abstract: Higher-order Petri nets are a class of high-level Petri nets, in which Petri nets themselves are first-class objects. Here tokens may represent Petri nets and Petri nets may be the values of parameters and variables, as well as the result of computations performed during the occurrence of transitions. These features facilitate a number of very powerful higher-order modelling techniques, making Petri nets much more flexible, compositional, and the resulting models more reusable. This work explores the usefulness of some of these techniques by looking at them from an application point of view and by illustrating them with small to medium-sized application examples.
TL;DR: The structural characteristics that a particular class of generalized stochastic Petri nets must exhibit in order for their stationary probabilities to have a product-form are shown.
Abstract: In this paper, we show the structural characteristics that a particular class of generalized stochastic Petri nets must exhibit in order for their stationary probabilities to have a product-form. Sufficient conditions for identifying such a class are derived and proven with the development of a series of transformations that can also be used to construct, for any GSPN of the class, an equivalent SPN. These resulting SPNs represent the structures that can be analyzed with standard methods for product-form SPNs to establish whether the original GSPNs have product-form solutions and to compute their performance indices with effective approaches based on computationally efficient algorithms that avoid the generation of their underlying state spaces.
25 Aug 2002
TL;DR: This paper considers formal modelling of event-driven real-time systems with Time Petri Nets with model-checking by a simple.
Abstract: The growing complexity of modern real-time embedded systems makes it imperative to apply formal analysis techniques at early stages of system development. This paper considers formal modelling of event-driven real-time systems with Time Petri Nets, and subsequent analysis via model-checking by a simple, fully automatable translation into Timed Automata. The proposed approach is applied to a small application scenario taken from Avionics Mission Computing.
Journal Article•
TL;DR: The paper discusses applicability of NP-nets for modeling task planning systems, multi-agent systems and recursive-parallel systems, and some aspects of decidability for object-oriented Petri net extensions are discussed.
Abstract: Nested Petri nets (NP-nets) is a Petri net extension, allowing tokens in a net marking to be represented by marked nets themselves The paper discusses applicability of NP-nets for modeling task planning systems, multi-agent systems and recursive-parallel systems A comparison of NP-nets with some other formalisms, such as OPNs of R Valk, recursive parallel programs of O Kushnarenko and Ph Schnoebelen and process algebras is given Some aspects of decidability for object-oriented Petri net extensions are also discussed
24 Jun 2002
TL;DR: An improved algorithm for computing the McMillan-unfolding of a time Petri net which gives a finite representation of the partial order semantics and some experimental results of its implementation within the PEP tool are presented.
Abstract: Recently, model checking of Petri nets based on partial order semantics w.r.t. temporal logic formulae has been extended to time Petri nets. In this paper, we present an improved algorithm for computing the McMillan-unfolding of a time Petri net which gives a finite representation of the partial order semantics and some experimental results of its implementation within the PEP tool.
08 Apr 2002
TL;DR: The aim of this paper is to give a mathematical foundation for design and analysis of multi-agent systems by means of a Petri-net-based model, called PN2, based on place/transition nets, which is one of the simplest classes of Petri nets.
Abstract: Agent technology is widely recognized as a new paradigm for design of concurrent software and systems. The aim of this paper is to give a mathematical foundation for design and analysis of multi-agent systems by means of a Petri-net-based model. The proposed model, called PN2, is based on place/transition nets (P/T nets), which is one of the simplest classes of Petri nets. The main difference between PN2s and P/T nets is that each token, representing an agent, is also a P/T net. State equation and invariants are known as standard techniques for the analysis of P/T nets. As the first step of mathematical analysis of PN2s, we define these for PN2s, and show how the invariants are computed in an efficient way.
Proceedings Article•
01 Jan 2002
TL;DR: Using the well-known example of the Beer Game, a systematic method supporting the bottom-up construction of re-usable models of supply chains in the Petri nets domain together with their associated experimental frames is presented.
Abstract: In this paper the authors propose an implementation of an incremental approach to modelling discrete event systems at the structural level of systems specification. Using the well-known example of the Beer Game, a systematic method supporting the bottom-up construction of re-usable models of supply chains in the Petri nets domain together with their associated experimental frames is presented. The construction adheres to well-defined rules, which would enable computer-based model generation.
23 Jun 2002
TL;DR: A stepwise approach for dependability modeling, based on Generalized Stochastic Petri Nets, that allows the various dependencies to be taken into account at the right level of abstraction: functional dependency, structural dependency and those induced by non-exponential distributions.
Abstract: This paper presents a stepwise approach for dependability modeling, based on Generalized Stochastic Petri Nets (GSPNs). The first-step model called functional-level model, can be built as early as system functional specifications and then completed by the structural model as soon as the system architecture is known, even at a very high level. The latter can be refitted according to three different aspects: component decomposition, state and event fine-tuning and distribution adjustment to take into account increasing event rates. We define specific rules to make the successive transformations as easy and systematic as possible. This approach allows the various dependencies to be taken into account at the right level of abstraction: functional dependency, structural dependency and those induced by non-exponential distributions. A part of the approach is applied to an instrumentation and control system (I&C) in power plants.
Journal Article•
TL;DR: The Asynchronous Box Calculus (ABC) as mentioned in this paper is a dual model based on Petri nets and process expressions, suitable for modelling and analysing distributed systems whose components can interact using both synchronous and asynchronous communication.
Abstract: The starting point of this paper is an algebraic Petri net framework allowing one to express net compositions, such as iteration and parallel composition, as well as transition synchronisation and restriction. We enrich the original model by introducing new constructs supporting asynchronous interprocess communication. Such a communication is made possible thanks to special 'buffer' places where different transitions (processes) may deposit and remove tokens. We also provide an abstraction mechanism, which hides buffer places, effectively making them private to the processes communicating through them. We then provide an algebra of process expressions, whose constants and operators directly correspond to those used in the Petri net framework. Such a correspondence is used to associate nets to process expressions in a compositional way. That the resulting algebra of expressions is consistent with the net algebra is demonstrated by showing that an expression and the corresponding net generate isomorphic transition systems. This results in the Asynchronous Box Calculus (or ABC), which is a coherent dual model, based on Petri nets and process expressions, suitable for modelling and analysing distributed systems whose components can interact using both synchronous and asynchronous communication.