Showing papers on "Process architecture published in 2005"

Applications and Theory of Petri Nets 2005

Abstract: Invited Papers.- Expressiveness and Efficient Analysis of Stochastic Well-Formed Nets.- Applications of Craig Interpolation to Model Checking.- Towards an Algebra for Security Policies.- Continuization of Timed Petri Nets: From Performance Evaluation to Observation and Control.- Full Papers.- Genetic Process Mining.- The (True) Concurrent Markov Property and Some Applications to Markov Nets.- On the Equivalence Between Liveness and Deadlock-Freeness in Petri Nets.- Extremal Throughputs in Free-Choice Nets.- A Framework to Decompose GSPN Models.- Modeling Dynamic Architectures Using Nets-Within-Nets.- A High Level Language for Structural Relations in Well-Formed Nets.- Derivation of Non-structural Invariants of Petri Nets Using Abstract Interpretation.- Modeling Multi-valued Genetic Regulatory Networks Using High-Level Petri Nets.- Termination Properties of TCP's Connection Management Procedures.- Soundness of Resource-Constrained Workflow Nets.- High-Level Nets with Nets and Rules as Tokens.- Can I Execute My Scenario in Your Net?.- Reference and Value Semantics Are Equivalent for Ordinary Object Petri Nets.- Particle Petri Nets for Aircraft Procedure Monitoring Under Uncertainty.- On the Expressive Power of Petri Net Schemata.- Determinate STG Decomposition of Marked Graphs.- Timed-Arc Petri Nets vs. Networks of Timed Automata.- Specifying and Analyzing Software Safety Requirements of a Frequency Converter Using Coloured Petri Nets.- Achieving a General, Formal and Decidable Approach to the OR-Join in Workflow Using Reset Nets.- Tool Papers.- The ProM Framework: A New Era in Process Mining Tool Support.- High Level Petri Nets Analysis with Helena.- Protos 7.0: Simulation Made Accessible.

Process Management: Why Project Management Fails in Complex Decision Making Processes

Abstract: 1. Prologue. 1.1. Introduction. 1.2. The process approach to change: a tentative description. 1.3. Stucture of the book. Notes. Part I: Introduction to Process Design and Process Management. 2. Positioning the process approach. 2.1. Introduction. 2.2. Process management versus substance. 2.3. Process management versus command and control. 2.4. Process management versus project management. 2.5. Process management versus single-value decision making. 2.6. The main arguments for process management. 2.7. The results of a process: consensus, commitment or tolerance. 2.8. The risks of process thinking. Part III: Process Architecture. 3.Designing a process. 3.1. Introduction. 3.2. The four core elements of a process design. 3.3. Design principles leading to open decision making. 3.4. Design principles protecting parties' core values. 3.5. Design principles guaranteeing the speed of the process. 3.6. Design principles guaranteeing the substance of the notes. Notes. 4: The Process Architect in Action: Making a Process Design. 4.1. Introduction. 4.2. The process design as a result of negotiation. 4.3. The need for a sense of urgency. 4.4. The process architect in action: designing a process. 4.5. Process management and related approaches. Notes. Part III: Managing the Process. 5.1. Introduction. 5.2. Involving parties in the decision making. 5.3. The transformation from substance to process. 5.4. Process and process management are marked by transparency and openness. Notes. 6. Process management and the protection of the parties'core values. 6.1. Introduction. 6.2. Protecting core values. 6.3. Commitment to the process and the result. 6.4. Postponing commitments during the process. 6.5. The exit rules of the process. Notes. 7. The process manager and the speed of decision making. 7.1. Introduction. 7.2. Incentives for cooperative behaviour. 7.3. The process has participants with commitment power. 7.4. Management of the environment. 7.5. Conflicts are transferred to the periphery of the process. 7.6. Command and control in a process: as a driver and as a result of the process. Notes. 8. The process manager and the substance of decision making. 8.1. Introduction. 8.2. Unbundling and bundling experts and stakeholders. 8.3. Intermezzo: strategic behaviour or sound and substantive behaviour? 8.4. The process from substantive variety to selection. Epilogue. References. Index. About the Authors.

A Petri Net Structure– Based Deadlock Prevention Solution for Sequential Resource Allocation Systems

Abstract: A new method for the deadlock prevention problem in concurrent systems where a set of processes share a set of common resources in a conservative way is proposed. It can be applied to flexible manufacturing systems, modeled with Petri nets. In this paper, we present a set of important results related to the deadlock prevention problem in S4PR nets. First, a liveness characterization is introduced, establishing how deadlocks can be studied in terms of circular waits. Second, we show how a circular wait situation corresponds to a particular marking related to a siphon of the Petri net model. Finally, this last characterization is used to obtain an iterative method that successively forbids deadlock related states, synthesizing the control necessary to ensure a final live behavior. The method can be implemented by means of the solutions of a set of integer linear programming problems.

Algebraic approaches for fault identification in discrete-event systems

Abstract: In this note, we develop algebraic approaches for fault identification in discrete-event systems that are described by Petri nets. We consider faults in both Petri net transitions and places, and assume that system events are not directly observable but that the system state is periodically observable. The particular methodology we explore incorporates redundancy into a given Petri net in a way that enables fault detection and identification to be performed efficiently using algebraic decoding techniques. The guiding principle in adding redundancy is to keep the number of additional Petri net places small while retaining enough information to be able to systematically detect and identify faults when the system state becomes available. The end result is a redundant Petri net embedding that uses 2k additional places and enables the simultaneous identification of 2k-1 transition faults and k place faults (that may occur at various instants during the operation of the Petri net). The proposed identification scheme has worst-case complexity of O(k(m+n)) operations where m and n are respectively the number of transitions and places in the given Petri net.

Analyzing BPEL processes using Petri nets

Abstract: Some years ago, BEA, IBM, Microsoft, SAP AG, and Siebel Systems teamed up and proposed the Business Process Execution Language for Web Services (BPEL or BPEL4WS) for application integration within and across organizational boundaries. By now, BPEL has become the de facto standard in this Web services composition arena. However, little effort has been dedicated so far concerning the verification of the modeled business processes. For example, there is no support to detect possible deadlocks, or to detect parts of the process that are not viable. For so-called WF-nets (workflow nets), techniques and tools exist which make it possible to detect such anomalies. Therefore, we could detect these anomalies in a BPEL process model provided that we can successfully map this model onto a WF-net. This papers describes a first attempt to map a BPEL process model onto a WF-net. Although not all BPEL constructs have been mapped yet, the results seem promising, as we are able to map typical examples from the BPEL 1.1 specification onto WF-nets.

A Petri Net Semantics for BPEL

Abstract: We present a pattern-based Petri net semantics for the Business Process Execution Language for Web Services (BPEL). Our semantics is complete – it covers the standard behaviour of BPEL as well as the exceptional behaviour (e.g. faults, events, compensation). Therefore every business process specified in BPEL can be transformed into a Petri net.

Structuring and composability issues in Petri nets modeling

Abstract: Along Petri nets' history, numerous approaches have been proposed that try to manage model size through the introduction of structuring mechanisms allowing hierarchical representations and model composability. This paper proposes a classification system for Petri nets' structuring mechanisms and discusses each one of them. These include node fusion, node vectors, high-level nets, and object-oriented inspired Petri nets extensions, among others. One running example is used emphasizing the application of the presented mechanisms to specific areas, namely to automation systems modeling, and software engineering, where object-oriented modeling plays a major role.

Compositional semantics for UML 2.0 sequence diagrams using petri nets

Abstract: With the introduction of UML 2.0, many improvements to diagrams have been incorporated into the language. Some of the major changes were applied to sequence diagrams, which were enhanced with most of the concepts from ITU-T's Message Sequence Charts, and more. In this paper, we introduce a formal semantics for most concepts of sequence diagrams by means of Petri nets as a formal model. Thus, we are able to express the partially ordered and concurrent behaviour of the diagrams natively within the model. Moreover, the use of coloured high-level Petri nets allows a comprehensive and efficient structure for data types and control elements. The proposed semantics is defined compositionally, based on basic Petri net composition operations.

Dynamic scheduling in flexible assembly system based on timed Petri nets model

Abstract: This paper investigates a scheduling model for optimal production sequencing in a flexible assembly system. The system features a set of machines working together in the same workspace, with each machine performing a subset of operations. Three constraints are considered: (1) the precedence relation among the operations specified by the assembly tree; (2) working space that limits concurrent operations; and (3) the variation of process time. The objective is to find both a feasible assignment of operations to machines and schedule tasks in order to minimize the completion time for a single product or a batch of products. The assembly process is modeled using timed Petri nets and task scheduling is solved with a dynamic programming algorithm. The method calculates the time required precisely. A detailed case study is discussed to show the effectiveness of the model and algorithm.

Time Petri Nets for Modelling and Analysis of Biochemical Networks

Abstract: Biochemical networks are modelled at different abstraction levels. Basically, qualitative and quantitative models can be distinguished, which are typically treated as separate ones. In this paper, we bridge the gap between qualitative and quantitative models and apply time Petri nets for modelling and analysis of molecular biological systems. We demonstrate how to develop quantitative models of biochemical networks in a systematic manner, starting from the underlying qualitative ones. For this purpose we exploit the well-established structural Petri net analysis technique of transition invariants, which may be interpreted as a characterisation of the system?s steady state behaviour. For the analysis of the derived quantitative model, given as time Petri net, we present structural techniques to decide the time-dependent realisability of a transition sequence and to calculate its shortest and longest time length. All steps of the demonstrated approach consider systems of integer linear inequalities. The crucial point is the total avoidance of any state space construction. Therefore, the presented technology may be applied also to infinite systems, i.e. unbounded Petri nets.

Time supervision of concurrent systems using symbolic unfoldings of time petri nets

Abstract: Monitoring real-time concurrent systems is a challenging task. In this paper we formulate (model-based) supervision by means of hidden state history reconstruction, from event (e.g. alarm) observations. We follow a so-called true concurrency approach using time Petri nets: the model defines explicitly the causal and concurrency relations between the observable events, produced by the system under supervision on different points of observation, and constrained by time aspects. The problem is to compute on-the-fly the different partial order histories, which are the possible explanations of the observable events. We do not impose that time is observable: the aim of supervision is to infer the partial ordering of the events and their possible firing dates. This is achieved by considering a model of the system under supervision, given as a time Petri net, and the on-the-fly construction of an unfolding, guided by the observations. Using a symbolic representation, this paper presents a new definition of the unfolding of time Petri nets with dense time.

Transformation BPEL to CP-nets for verifying Web services composition

Abstract: Web services composition is an emerging paradigm for enabling application integration within and across organizational boundaries. Business process execution language (BPEL) is a promising language describing the Web services composition in form of business processes, but lack of a sound formal semantic, which hinders the formal analysis and verification of business processes specified in it. This paper presents the transformation of BPEL to colored Petri nets (CP-nets) in a constructive way. Therefore we can translate composition specified in BPEL into CP-nets, which can be analyzed and verified by many specialized tools. So we make tool support available for verifying BPEL composition.

Modular Petri Net based modeling, analysis, synthesis and performance evaluation of random topology dedicated production systems

Abstract: Ordinary t-timed modular Petri Nets are used for modeling, analysis, synthesis and performance evaluation of random topology dedicated production systems. Each system is first decomposed into production line, assembly, disassembly and parallel machine modules followed by derivation of their modular Petri Net models. Two sets of modules, generic and generalized respectively, are derived corresponding to the simplest and most general cases. Overall system Petri Net model is obtained via synthesis of the individual modules satisfying system features (production rates, buffer capacities, machine expected up, down or idle times). Detailed mathematical expressions are derived for modules P-invariants (and T-invariants when exist); they are further generalized for a random topology and complexity dedicated production system. Total number of the individual Petri Net module nodes as well as of the combined system Petri Net model is also calculated. Results show the applicability of the proposed methodology and justify its modeling power and generality.

Identification of free-labeled Petri nets via integer programming

Abstract: In this paper we deal with the problem of identifying a Petri net system, given a finite language that it generates. In particular, we consider the problem of identifying a free-labeled Petri net system, i.e., a net system where each transition is assigned a unique label. We show that the identification problem can be solved via an integer programming problem. We also discuss how additional structural constraints can be easily imposed to the net.

Modeling multi-valued genetic regulatory networks using high-level petri nets

Abstract: Regulatory networks are at the core of all biological functions from bio-chemical pathways to gene regulation and cell communication processes. Because of the complexity of the interweaving retroactions, the overall behavior is difficult to grasp and the development of formal methods is needed in order to confront the supposed properties of the biological system to the model. We revisit here the tremendous work of R. Thomas and show that its binary and also its multi-valued approach can be expressed in a unified way with high-level Petri nets. A compact modeling of genetic networks is proposed in which the tokens represent gene's expression levels and their dynamical behavior depends on a certain number of biological parameters. This allows us to take advantage of techniques and tools in the field of high-level Petri nets. A developed prototype allows a biologist to verify systematically the coherence of the system under various hypotheses. These hypotheses are translated into temporal logic formulae and the model-checking techniques are used to retain only the models whose behavior is coherent with the biological knowledge.

Timed-arc petri nets vs. networks of timed automata

Abstract: We establish mutual translations between the classes of 1-safe timed-arc Petri nets (and its extension with testing arcs) and networks of timed automata (and its subclass where every clock used in the guard has to be reset). The presented translations are very tight (up to isomorphism of labelled transition systems with time). This provides a convenient characterization from the theoretical point of view but is not always satisfactory from the practical point of view because of the possible non-polynomial blow up in the size (in the direction from automata to nets). Hence we relax the isomorphism requirement and provide efficient (polynomial time) reductions between networks of timed automata and 1-safe timed-arc Petri nets preserving the answer to the reachability question. This makes our techniques suitable for automatic translation into a format required by tools like UPPAAL and KRONOS. A direct corollary of the presented reductions is a new PSPACE-completeness result for reachability in 1-safe timed-arc Petri nets, reusing the region/zone techniques already developed for timed automata.

Correctness verification and performance analysis of real-time systems using stochastic preemptive time Petri nets

Abstract: Time Petri nets describe the state of a timed system through a marking and a set of clocks. If clocks take values in a dense domain, state space analysis must rely on equivalence classes. These support verification of logical sequencing and quantitative timing of events, but they are hard to be enriched with a stochastic characterization of nondeterminism necessary for performance and dependability evaluation. Casting clocks into a discrete domain overcomes the limitation, but raises a number of problems deriving from the intertwined effects of concurrency and timing. We present a discrete-time variant of time Petri nets, called stochastic preemptive time Petri nets, which provides a unified solution for the above problems through the adoption of a maximal step semantics in which the logical location evolves through the concurrent firing of transition sets. We propose an analysis technique, which integrates the enumeration of a succession relation among sets of timed states with the calculus of their probability distribution. This enables a joint approach to the evaluation of performance and dependability indexes as well as to the verification of sequencing and timeliness correctness. Expressive and analysis capabilities of the model are demonstrated with reference to a real-time digital control system.

A Survey of Object-Oriented Petri Nets and Analysis Methods

Abstract: Petri nets are a well-known graphical and modeling tool for concurrent and distributed systems, and there have been many results on the theory, and also on practical applications. In the last decade, various Object-Oriented Petri nets (OO-nets) are proposed. As object orientation was adopted for programming languages, extension to OO-nets inspired from object-oriented programming is a natural flow. This article presents state-of-the-art on OO-nets.

The individual and collective token interpretations of Petri nets

Abstract: Starting from the opinion that the standard firing rule of Petri nets embodies the collective token interpretation of nets rather than their individual token interpretation, I propose a new firing rule that embodies the latter. Also variants of both firing rules for the self-sequential interpretation of nets are studied. Using these rules, I express the four computational interpretations of Petri nets by semantic mappings from nets to labelled step transition systems, the latter being event-oriented representations of higher dimensional automata. This paper totally orders the expressive power of the four interpretations, measured in terms of the classes of labelled step transition systems up to isomorphism of reachable parts that can be denoted by nets under each of the interpretations. Furthermore, I extend the unfolding construction of place/transition nets into occurrence net to nets that may have transitions without incoming arcs.

A threat-driven approach to modeling and verifying secure software

Abstract: This paper presents a formal approach to threat-driven modeling and verification of secure software using aspect-oriented Petri nets Based on the behavior model of intended functions, we identify and build formal models of security threats, which are potential misuses and anomalies of the intended functions that violate security goals Threat mitigations are further modeled in an aspect-oriented paradigm Taking Petri nets as a formal basis for modeling behaviors, threats, and mitigations as a whole, we verify properties of and consistency between behaviors and threats, and absence of identified threats from the integrated model of functions and threat mitigations This makes it possible to achieve a design that is provably resistant to the anticipated threats and thus reduce significant design-level vulnerabilities

An augmented Petri Net approach for error recovery in manufacturing systems control

Abstract: The construction of error recovery Petri subnets and similar representations have received considerable attention in the literature. Previous work has presented a multi-agent system representing various levels of control in a reconfigurable architecture. Agents pertaining to production, mediation, and error recovery within such an architecture were considered. Our focus here is on the workstation level of a hierarchy where the workstation has the capability for recovery from physical errors. The implications of error recovery tasks from the perspective of control are also discussed. The approach is based on integrating Petri subnet models within a general Petri Net model for a manufacturing system environment. In essence, the error recovery plan consists of a trajectory (Petri subnet) having the detailed recovery steps that are then incorporated into the workstation control logic. The logic is based on a Timed Petri Net model of the total production system. The Petri subset models consist of a sequence of steps required to reinstate the system back to a normal state. Once generated, the recovery subnet is incorporated into the Petri Net model of the original expected (error-free) model. Petri Net augmentations pertaining to various issues are discussed in detail throughout the paper. Issues include the implication of generated error recovery trajectories in the production activities, linking of production activity Net and the error recovery subnet, potential deadlocks, the role of resources, and part handling.

Petri net-based workflow modelling and analysis of the integrated manufacturing business processes

Abstract: The well-behaved properties in workflow systems are very important for business processes. In this paper, a structured business process modelling approach by using free-choice Petri nets and workflow analysis techniques is proposed. This approach can be used to verify the soundness of workflow process specification for finding control-flow errors in the designs. For example, deadlock and dangling tasks in process models can be avoided by using this approach. However, for arbitrary Petri nets, the checking of sound properties is a NP-hard problem. This paper presents a structured business process modelling algorithm. This algorithm employs six well-behaved control structures, chaining rule and modified nesting rule to construct well-behaved process models. The resulting process models from this algorithm are free-choice workflow-nets, for which sound property can be decided in polynomial time. The proposed method is an extension of the workflow-net. The basic transformation rules in the workflow-net are subsets of the proposed nesting rule in this paper. The process models resulted from this structured business process modelling algorithm also have the advantages of modularity, readability and maintainability.

A framework for classifying and evaluating process architecture methods

Abstract: Piecemeal identification, development, and support of an organisation's processes may lead to problems: first, it may be difficult to identify which processes should be supported, and, second, it is unlikely that processes developed piecemeal will either optimise the achievement of an organisation's objectives, or work well together. One solution involves identifying and modelling an organisation's process architecture, and then using it to develop and subsequently support the constituent processes. However, this solution leads to a new challenge: a number of different types of process architecture method have been proposed, but it is not clear which should be used in a given situation. To address this challenge, the article outlines a framework for classifying, evaluating, and comparing process architectures. Following the work of Rolland et al.(1998), the proposed framework considers process architecture methods from four different views: contents, form, purpose, and lifecycle. To partially validate the framework, it was used to classify and evaluate Riva (Ould 2005), a particular process architecture method. The result of this application of the framework suggests how it might be refined. It could then be used for comparing other process architecture methods. Such a comparative analysis should help practitioners choose between process architecture methods. Copyright © 2005 John Wiley & Sons, Ltd.

Towards usage of formal methods within embedded systems co-design

Abstract: This paper presents the planned and on-going activities inside the FORDESIGN research project, funded by the Portuguese FCT (Foundation for Science and Technology), whose main objective is to foster the effective use of formal methods for embedded systems co-design. The project proposes a methodology where the use-cases are used as a starting point, not only for capturing requirements but also to support sub-model compositions. The methodology will support several different graphical formalisms, namely state diagrams, hierarchical and concurrent state diagrams, state-charts, sequence diagrams, and Petri nets. The latter are also used as the interchange format between the other used graphical formalisms. Hence, translations to Petri nets play a fundamental role. These Petri nets are then implemented using hardware-software co-design techniques, which will include reconfigurable devices, as well as microcontroller architectures, as supporting platforms. The project also includes the definition of a generic mechanism for Petri nets composition. This will offer support for composition, hierarchical structuring, and model modification