Showing papers on "Process architecture published in 2015"

Design of Optimal Petri Net Controllers for Disjunctive Generalized Mutual Exclusion Constraints

Abstract: In this paper, a type of specifications called OR-AND Generalized Mutual Exclusion Constraints (GMEC) for place/transition nets is defined. Such a specification consists of a disjunction of conjunction of several single GMECs, i.e., the requirement is that, at any given time, the controlled system should satisfy at least one set of conjunctive GMECs. We show that a bounded OR-AND GMEC can be enforced by a special control structure composed by a set of AND-GMEC monitor places plus a switcher that determines the current active ones. We also show that such a simple control structure can be modified to ensure maximal permissiveness. This approach can be used in the framework of supervisory control in Petri nets.

A Petri Net-Based Discrete-Event Control of Automated Manufacturing Systems With Assembly Operations

Abstract: In the context of automated manufacturing systems (AMSs), Petri nets are widely adopted to solve the modeling, analysis, and control problems. So far, nearly all known approaches to liveness-enforcing supervisory control study AMSs with flexible routes, whereas little work investigates the ones with synchronization operations. Compared with flexibility, synchronization allows the disassembly and assembly operations that correspond to splitting to and merging from different subprocesses, respectively. Such structures bring difficulties to establish a liveness condition of the Petri net model of AMSs. In this paper, we propose a novel class of systems, which can well deal with these features so as to facilitate the investigation of such complex systems. Using structural analysis, we show that their liveness can be attributed to deadlock freeness, which is much easier to analyze, detect, and control by synthesizing a proper supervisory controller. Furthermore, a set of mathematical formulations is proposed to describe and extract the corresponding deadlocks. This facilitates the synthesis of liveness enforcing supervisors as it avoids the consideration of deadlock-free but nonlive scenarios. The effectiveness and efficiency of this new method is shown by AMS examples.

Petri Net Synthesis

Abstract: This book is a comprehensive, systematic survey of the synthesis problem, and of region theory which underlies its solution, covering the related theory, algorithms, and applications. The authors focus on safe Petri nets and place/transition nets (P/T-nets), treating synthesis as an automated process which, given behavioural specifications or partial specifications of a system to be realized, decides whether the specifications are feasible, and then produces a Petri net realizing them exactly, or if this is not possible produces a Petri net realizing an optimal approximation of the specifications. In Part I the authors introduce elementary net synthesis. In Part II they explain variations of elementary net synthesis and the unified theory of net synthesis. The first three chapters of Part III address the linear algebraic structure of regions, synthesis of P/T-nets from finite initialized transition systems, and the synthesis of unbounded P/T-nets. Finally, the last chapter in Part III and the chapters in Part IV cover more advanced topics and applications: P/T-net with the step firing rule, extracting concurrency from transition systems, process discovery, supervisory control, and the design of speed-independent circuits. Most chapters conclude with exercises, and the book is a valuable reference for both graduate students of computer science and electrical engineering and researchers and engineers in this domain.

Stochastic Petri Net Modeling, Simulation and Analysis of Public Bicycle Sharing Systems

Abstract: Public Bicycle-Sharing Systems (PBSS) have been appearing in more and more cities around the world in the last few years. Although their apparent success as an alternative form of public transportation mode, there are major challenges confronting the operators while few scientific works are available to support such complex dynamical systems to influence their economic viability and operational efficiency. One of the most crucial factors for the success of a PBS system is its ability to ensure that bicycles are available for pick up and vacant berths available for bicycle drop off at every station. In this paper, we develop an original discrete event approach for modelling and performance evaluation of public bicycle-sharing systems by using Petri nets with time, inhibitor arcs and variable arc weights.

Petri nets in systems biology

Abstract: Petri nets are used in many areas. This article discusses the application of Petri nets in systems biology. Using an example from biochemistry, concepts for the automatic decomposition of biochemical systems are introduced. The article focuses on those concepts that fulfill steady-state conditions. Interestingly, all the concepts are based on minimal, semi-positive transition invariants. The article describes, which new definitions for network decomposition can be derived and how they can be interpreted in the context of biology. This is illustrated with the example of the citric acid cycle, for which a new metabolic pathway could be predicted with the help of such an analysis.

A Survey of Petri Net Tools

Abstract: Petri net is a mathematical modeling language used to describe a system graphically. It is a strong language that can be used to represent parallel or concurrent activities in a system. With a Petri net tool, users can view the overall system graphically and edit it with the editor. A Petri net tool can also be used to analyze the performance of the system, generate code, simulate the system and perform model checking on it. A review on twenty Petri net tools in this paper will give the readers an idea on what is a Petri net tool and the main functions of a Petri net tool. This paper can serve as an introduction of twenty Petri net tools to the reader. However, to date, there are many Petri net tools available to be downloaded online. This survey paper aims to compare twenty Petri net tools in different aspect. This is important as users will not have to read the reviews of Petri net tools online one by one. Just be having a look at the discussion provided, readers can determined the best recommended Petri net tools to be used based on their operating systems and the types of Petri net tool to be analyzed. The main purpose of this survey paper is to recommend Petri net tools based on the operating system and the types of Petri net to be analyzed.

Charlie – An Extensible Petri Net Analysis Tool

Abstract: Charlie is an extensible thread-based Java tool for analysing Petri nets. Its built-in functionalities apply standard analysis techniques of Petri net theory (e.g. invariants, siphon/trap property) to determine structural and behavioural properties of place/transition Petri nets, complemented by explicit CTL and LTL model checking. Charlie comes with a plugin mechanism, which permits to easily extend its basic functionality as it has been demonstrated for, e.g., structural reduction and time-dependent Petri nets. Charlie’s primary focus is teaching. For thispurpose, it has a rule system comprising standard theorems of Petri net theory to possibly decide further properties based on the already determined ones. All applied rules are reported by default, so the user may keep track of all analysis steps. The tool is in use for model verification of technical systems, especially software-based systems, as well as for model validation of natural systems, i.e. biochemical networks, such as metabolic, signal transduction, and gene regulatory networks. It is publicly available at http://www-dssz.informatik.tu-cottbus.de/DSSZ/Software/Charlie.

SNAKES: A Flexible High-Level Petri Nets Library (Tool Paper)

Abstract: SNAKES (SNAKES is the Net Algebra Kit for Editors and Simulators) is a general purpose Petri nets library, primarily for the Python programming language but portable to other ones. It defines a very general variant of Python-coloured Petri nets that can be created and manipulated through the library, as well as executed to explore state spaces. Thanks to a variety of plugins, SNAKES can handle extensions of Petri nets, in particular algebras of Petri nets [4, 26]. SNAKES ships with a compiler for the ABCD language that is precisely such an algebra. Finally, one can use the companion tool Neco [14] that compiles a Petri net into an optimised library allowing to compute efficiently its state space or perform LTL model-checking thanks to library SPOT [8, 13]. This paper describes SNAKES’ structure and features.

Complexity Analysis of Continuous Petri Nets

Abstract: At the end of the eighties, continuous Petri nets were introduced for: 1 alleviating the combinatory explosion triggered by discrete Petri nets i.e. usual Petri nets and, 2 modelling the behaviour of physical systems whose state is composed of continuous variables. Since then several works have established that the computational complexity of deciding some standard behavioural properties of Petri nets is reduced in this framework. Here we first establish the decidability of additional properties like coverability, boundedness and reachability set inclusion. We also design new decision procedures for reachability and lim-reachability problems with a better computational complexity. Finally we provide lower bounds characterising the exact complexity class of the reachability, the coverability, the boundedness, the deadlock freeness and the liveness problems. A small case study is introduced and analysed with these new procedures.

Business process management as the Killer App for Petri nets

Abstract: Since their inception in 1962, Petri nets have been used in a wide variety of application domains. Although Petri nets are graphical and easy to understand, they have formal semantics and allow for analysis techniques ranging from model checking and structural analysis to process mining and performance analysis. Over time Petri nets emerged as a solid foundation for Business Process Management (BPM) research. The BPM discipline develops methods, techniques, and tools to support the design, enactment, management, and analysis of operational business processes. Mainstream business process modeling notations and workflow management systems are using token-based semantics borrowed from Petri nets. Moreover, state-of-the-art BPM analysis techniques are using Petri nets as an internal representation. Users of BPM methods and tools are often not aware of this. This paper aims to unveil the seminal role of Petri nets in BPM.

Context-adaptive Petri nets

Abstract: We propose context-adaptive Petri nets (CAPN).CAPN allows the modeling of systems that need to adapt to their execution context.CAPN deals with data and system behavior as separate concerns.A tool is developed to support the modeling, simulation, and execution of CAPN.We thoroughly evaluate CAPN showing its benefits and further challenges. Petri nets (PNs) are a mathematical and graphical modeling language with powerful analysis techniques. They have been successfully used in several areas, such as business process management, human computer interaction, and pervasive computing. Within these areas, context adaptivity has recently emerged as a new challenge to explicitly address fitness between system behavior and its execution context. However, the existing PN formalisms do not provide reliable modeling, simulation, and verification techniques that can accurately consider the system's execution context and adapt to it in order to reflect the system execution reality. This paper addresses this problem by presenting context-adaptive Petri nets (CAPNs), a formalism that allows the modeling of context-adaptive behavior by integrating the powerful modeling and analysis techniques of PNs with very expressive context data management techniques. The formalism is supported by a tool that allows its modeling, simulation, and verification. The contributions have been validated using a case-based evaluation showing very promising results. CAPNs will allow organizations to accurately describe, enact, and analyze the behavior of their dynamic systems in a more reliable and realistic way, allowing them to leverage more informed decisions, to make better use of their resources, and to increase therefore their competitiveness.

A Polynomial Algorithm to Performance Analysis of Concurrent Systems Via Petri Nets and Ordinary Differential Equations

Abstract: In this paper, a new method is proposed to evaluate the performance of concurrent systems. A concurrent system consisting of multiple processes that communicate via message passing mechanisms is modeled by a Petri net, which is in turn represented by a set of ordinary differential equations (ODEs) of a restricted type. The equations describe the system state changes, and the solutions, also called state measures, can be used for the performance analysis such as estimating response time, throughput and efficiency. This method can avoid a state explosion problem encountered by the conventional methods based on Continuous-Time Markov Chains. Its application to an IBM business system is given as an example.

BioModel Engineering with Petri Nets

Abstract: We present a unifying Petri net framework comprising the qualitative, stochastic, continuous, and hybrid paradigm for modeling and analyzing biological reaction networks. By means of a running case study, we demonstrate how the different paradigms contribute in complementary ways to the overall understanding of emergent network properties. The framework is supported by four tools—Snoopy, Charlie, Marcie, and MC2—which will also be of use in the suggested exercises.

Supervisor Synthesis and Performance Improvement for Automated Manufacturing Systems by Using Petri Nets

Abstract: For event-driven systems like automated manufacturing systems (AMSs), intelligent part dispatching, i.e., to assign various parts to proper processing routes, is crucial to gain high resource utilization and production efficiency. This work proposes an innovative dispatching mechanism, which can better these metrics by minimizing the cycle time, i.e., the mean time to produce a product, while avoiding any deadlock, i.e., no part can proceed due to circuit wait. Its prerequisite is liveness supervision; however, temporal information is associated to certain operation stages for the sake of performance evaluation and throughput maximization, i.e., to maximize the finished-part quantity per time unit. In the paradigm of Petri nets, we show the criticality to prioritize certain activities locally. Our method can well design ratio parameters among distinct processes to improve system productivity.

Specifying and verifying real-time self-adaptive systems

Abstract: Self-adaptive systems autonomously adapt their behavior at run-time to react to internal dynamics and to uncertain and changing environment conditions. Specification and verification of self-adaptive systems are generally very difficult to carry out due to their high complexity, especially when involving time constraints. In the last case, in fact, the correctness of systems depends also on the time associated with events. This paper introduces a formal approach to specify and verify the self-adaptive behavior of real-time systems. Our specification formalism is based on Time-Basic Petri nets, a particular timed extension of Petri nets. We propose adaptation models to realize self-adaptation with temporal constraints and we adopt a zone-based modeling approach to support separation of concerns during the modeling phase. Zones identified during the modeling phase can be then used as modules (TB Petri subnets) either in isolation, to verify intra-zone properties, or all together, to verify inter-zone properties over the entire system model and check that all the temporal deadlines are met. We illustrate our approach by modeling and verifying a time-critical Gas Burner system that exhibits a self-healing behavior.

Analysis of Petri Nets and Transition Systems

Abstract: This paper describes a stand-alone, no-frills tool supporting the analysis of (labelled) place/transition Petri nets and the synthesis of labelled transition systems into Petri nets. It is implemented as a collection of independent, dedicated algorithms which have been designed to operate modularly, portably, extensibly, and efficiently.

Modeling DevOps Deployment Choices Using Process Architecture Design Dimensions

Abstract: DevOps is a software development approach that enables enterprises to rapidly deliver software product features through process automation, greater inter-team collaboration and increased efficiency introduced through monitoring and measuring activities. No two enterprise-adopted DevOps approaches would be similar as each enterprise has unique characteristics and requirements. At present, there is no structured method in enterprise architecture modeling that would enable enterprises to devise a DevOps approach suitable for their requirements while considering possible process reconfigurations. Any DevOps implementation can have variations at different points across development and operational processes and enterprises need to be able to systematically map these variation points and understand the trade-offs involved in selecting one alternative over another. In this paper, we use our previously proposed Business Process Architecture modeling technique to express and analyze DevOps alternatives and help enterprises select customized DevOps processes that match their contexts and requirements.

Robust supervisor synthesis for automated manufacturing systems using Petri nets

Abstract: In order to engage automated manufacturing systems in practice, a prerequisite is that they must be immune to deadlocks, which have been extensively investigated for decades by numerous researchers. To ease their effort, resources are presumptively and arbitrarily assumed never to fail; nevertheless, this is quite the opposite in reality. Actually, failures occur frequently due to various causes. In this paper, resource failures will be taken into consideration. In the paradigm of Petri nets, a robust control supervisor is developed to guarantee that the system will not be in stagnation when failures occur unexpectedly. Processes not requiring the failed resources can continue their progress smoothly. Three algorithms are proposed to achieve the tractability in deadlock-freeness, robustness, and concurrency matters, respectively. At each state, they are executed in sequence so as to attain a set of fireable transitions. Anyone of them is legal to fire by obeying these three properties. As a consequence, an appropriate firing sequence is derived so as to lead the system to a desired state. Experimental results show that the proposed approach is effective in response to resource failures.

A Reference Model for Software Agility Assessment: AgilityMod

Abstract: In this paper, we present AgilityMod that we developed with the purpose of identifying agility levels of software development projects, indicating agility gaps and providing roadmaps to organizations in adopting agile principles/practices. AgilityMod shares the meta-model structure of ISO/IEC 15504, software process assessment model, however, it differentiates from ISO/IEC 15504 in terms of its process architecture, process descriptions and description of other model elements. In this paper, we focus on the structure of the Model and describe the development stages of the Model. In addition, we briefly present a multiple case study that included eight cases, which was conducted to identify applicability and suitability of the Model.

Petri nets for the control of discrete event systems

Abstract: The interest in Petri nets has grown within the automatic control community in parallel with the development of the theory of discrete event systems. In this article, our goal is to give a flavor of the features that make Petri nets a good model for discrete event systems and to point out the main areas where Petri nets have offered the most significant contributions.

Verification of current-state opacity using Petri nets

Abstract: This paper addresses the problem of current-state opacity of discrete event systems (DES) modeled with Petri nets A system is said to be current-state opaque if the intruder who only has partial observations on the system's behavior is never able to infer that the current state of the system is within a set of secret states Based on the notion of basis markings, an efficient approach to verifying current-state opacity in bounded Petri nets is proposed, without computing the whole reachability set or exhaustively enumerating the set of markings consistent with the observation An example showing the efficiency of the approach is presented

Semantics for Consistent Activation in Context-Oriented Systems

Abstract: Context: Context-oriented programming languages provide dedicated programming abstractions to define behavioral adaptations and means to combine those adaptations dynamically according to sensed context changes. Some of these languages feature programming abstractions to explicitly define interaction dependencies among contexts. However, the semantics of context activation and the meaning of dependency relations have been described only informally, which in some cases has led to incorrect specifications, faulty implementations and inconsistent system behavior. Objective: With the aim of avoiding faulty implementations and inconsistencies during system execution, this paper proposes both a formal and run-time model of contexts, context activation and context interaction. Method: As a formal and computational basis, we introduce context Petri nets, a model based on Petri nets, which we found to match closely the structure of contexts in context-oriented systems. The operational semantics of Petri nets permits the modeling of run-time context activations, and existing Petri net analyses allow to reason about system properties. As validation, we carried out small and medium-sized case studies. Results: In the explored cases, Context Petri nets served effectively as underlying run-time model to ensure that declared context interaction constraints remain consistent during context manipulation. Moreover, context Petri nets enabled us to analyze certain properties regarding the activation state of particular contexts. Conclusion: Context Petri nets thus proved to be an appropriate formalism to encode and manage the semantics of context activation, both formally and computationally, so as to preserve the consistency of context-oriented systems.

Synthesis of Bounded Choice-Free Petri Nets

Abstract: This paper describes a synthesis algorithm tailored to the construction of choice-free Petri nets from finite persistent transition systems. With this goal in mind, a minimised set of simplified systems of linear inequalities is distilled from a general region-theoretic approach, leading to algorithmic improvements as well as to a partial characterisation of the class of persistent transition systems that have a choice-free Petri net realisation.

Adaptive e-learning system based on agents and object petri nets AELS-A/OPN

Abstract: Agent technology plays an important role in today's software development at the industrial level and brings advantages to the development of educational applications. The main focus of the multi-agent systems community has been on the development of concepts, architectures, interaction techniques, and general approaches to the analysis and specification of multi-agent systems. We introduce herein a novel concept involving the development of an e-Learning system architecture that explores several recent technologies, including multi-agent technology and adaptive e-Learning. The main concern of our research is twofold: to build a multi-agent architecture that provides the ability to adapt to the learner's preferences in the e-Learning environment and to analyze and control the communication and interactions among the different agents of the proposed system. Toward this aim, we present a distributed intelligent blackboard agent that ensures the communication among the participating agents. Furthermore, we describe a formal model that can be used to specify the message exchanges and their synchronization using Object Petri Nets. An exploratory implementation has been developed and conducted in practice. © 2013 Wiley Periodicals, Inc. Comput Appl Eng Educ 23:170–190, 2015; View this article online at wileyonlinelibrary.com/journal/cae; DOI 10.1002/cae.21587

Formal Modeling of Grafcets With Time Petri Nets

Abstract: Grafcet standard (IEC60848) is a formalism used in the world of manufacturing control, at the behavioral specification stage of a system. For specifying safe-critical systems, mathematical models associated with model-checking tools are necessary for the validation of the correctness. However, grafcets (meaning grafcet diagrams) are only semiformal models since certain aspects may be a source of different interpretations. The usual practice is to go through an intermediate formalism. In this brief, time Petri nets (TPNs) are chosen because they combine simplicity with wide-spreading and they also allow quantitative time analyses useful for the verification of real-time specifications. The main goal is to propose a principle of transforming a grafcet into TPN and to define the rules of this translation. The obstacle to overcome is to conciliate synchronous semantics of grafcet with asynchronous semantics of TPN.

Evaluation of an Atmosphere Revitalization Subsystem for Deep Space Exploration Missions

Abstract: An Atmosphere Revitalization Subsystem (ARS) suitable for deployment aboard deep space exploration mission vehicles has been developed and functionally demonstrated. This modified ARS process design architecture was derived from the International Space Station's (ISS) basic ARS. Primary functions considered in the architecture include trace contaminant control, carbon dioxide removal, carbon dioxide reduction, and oxygen generation. Candidate environmental monitoring instruments were also evaluated. The process architecture rearranges unit operations and employs equipment operational changes to reduce mass, simplify, and improve the functional performance for trace contaminant control, carbon dioxide removal, and oxygen generation. Results from integrated functional demonstration are summarized and compared to the performance observed during previous testing conducted on an ISS-like subsystem architecture and a similarly evolved process architecture. Considerations for further subsystem architecture and process technology development are discussed.

Learning material flow models for manufacturing plants from data traces

Abstract: Models describing the material flow of discrete manufacturing systems are important documentation artefacts and the basis for a comprehensive understanding of the underlying processes. The analysis of such models allows deriving important key performance indicators enabling the assessment of the current system implementation. However, manual modeling as well as up-to-date model maintenance is an error-prone and costly task. In an effort to allow for the automatic derivation of material flow models, this paper introduces the concept of Material Flow Petri Nets (MFPNs) and presents a learning algorithm for their automatic generation based on recorded PLC I/O data. The proposed algorithm has been evaluated on a case study of a laboratory plant with successful results.

Modeling of Safety-Critical Systems Using Petri Nets

Abstract: Safety plays a crucial role in the development of complex computer systems in the relevant areas like railway transport, process industry, power plants, etc. In the design phase of safety-critical systems, various methods are used to make the system work correctly. Due to advancements in technology, safety-critical systems are equipped with the necessary safety precautions but not completely. The malfunctioning of systems may lead to catastrophic accidents. Compared to commonly used safety-analysis approaches like Failure Mode and Effects Analysis, Fault Tree Analysis, Event Tree Analysis, etc., Petri Nets are more suitable for hazard analysis as they can specify data flow and stochastic interdependencies. An example safety-critical system, Railroad Crossing Junction has been modeled using Petri Nets for hazard analysis to detect the occurrences of possible hazards in the system. The proposed modeling framework provides a flexible graphical representation allowing a qualitative analysis based on the safe and unsafe state representations and a quantitative analysis based on the reachability graph that in turn leads to an effective safety analysis. The result of careful and rigorous safety analysis is to identify unsafe states. The results of safety analysis can be used by the designer for re-designing the system to improve safety. The designer of the system needs to repeat the process to detect the unsafe states.