Showing papers on "Petri net published in 2020"
TL;DR: Experimental results verify that the proposed deep Q-network with a PNC network can provide better solutions for dynamic scheduling problems in terms of manufacturing performance, computational efficiency, and adaptability compared with heuristic methods and a DQN with basic multilayer perceptrons.
102 citations
TL;DR: A hybrid formalism is proposed that strengthens SPN with BN capabilities and provides a dynamic assessment of safety by capturing additional sets of data rends and uses advance feature such as predicates to perform the data updating functions.
65 citations
TL;DR: A fault diagnosis model based on fuzzy Petri net (FPN) technique is developed that employs discrete evidences, such as status of protective devices and FIs to estimate the faulted section and a mismatch index is defined to eliminate the possible false fault section estimations.
Abstract: This paper proposes a hybrid fault location method for smart distribution systems by using available multi-source data, including data from protective devices, fault indicators (FIs), smart meters, voltage and current meters, and computer simulations. A fault diagnosis model based on fuzzy Petri net (FPN) technique is developed that employs discrete evidences, such as status of protective devices and FIs to estimate the faulted section. To eliminate the possible false fault section estimations and pinpoint the actual location of the fault a mismatch index is defined. It quantifies the similarity between recorded measurements, such as voltage and current signals during faults and the corresponding values obtained by performing short circuit analysis. The fault scenario with minimum mismatch degree is determined as the actual location of the fault. The proposed method can precisely determine the fault location in distribution systems with many laterals and sub-laterals with heterogenous line parameters in the presence of distributed generators (DGs). The accuracy and effectiveness of the proposed method are validated by applying the proposed method to the simulated IEEE 33 node feeder distribution system.
62 citations
TL;DR: Four iterated greedy algorithm-based methods by using different neighborhood structures and integrating a variable neighborhood descent method are developed to solve the scheduling problem of a batch production process, i.e., wire rod and bar rolling, which is modeled by a Petri net (PN).
Abstract: Wire rod and bar rolling is an important batch production process in steel production systems. A scheduling problem originated from this process is studied in this work by considering the constraints on sequence-dependent family setup time and release time. For each serial batch to be scheduled, it contains several jobs and the number of late jobs within it varies with its start time. First, we model a rolling process using a Petri net (PN), where a so-called rolling transition describes a rolling operation of a batch. The objective of the concerned problem is to determine a firing sequence of all rolling transitions such that the total number of late jobs is minimal. Next, a mixed-integer linear program is formulated based on the PN model. Due to the NP-hardness of the concerned problem, iterated greedy algorithm (IGA)-based methods by using different neighborhood structures and integrating a variable neighborhood descent method are developed to obtain its near-optimal solutions. To test the accuracy, speed, and stability of the proposed algorithms, we compare their solutions of different-size instances with those of CPLEX (a commercial software) and four heuristic peers. The results indicate that the proposed algorithms outperform their peers and have great potential to be applied to industrial production process scheduling.
61 citations
TL;DR: A formal framework to assess the safety and efficiency of maintenance strategies by means of agent-based modelling, stochastically and dynamically coloured Petri nets, and Monte Carlo simulation is proposed.
50 citations
TL;DR: A cloud model based on interval-valued intuitionistic uncertain linguistic and builds a cloud-based Petri net model to assess the risk of subway fire accident of subway, using fuzzy linguistic decision variables is proposed.
Abstract: This article proposes a risk assessment method based on interval intuitionistic integrated cloud Petri net (IIICPN). The cloud model is widely used in data mining and knowledge discovery, especially in risk assessment problems with linguistic variables. However, the cloud models proposed in the literature do not express interval-valued intuitionistic linguistic satisfactorily, and the reasoning methods based on the cloud models cannot perform risk assessment well. The work in this article includes the definition of IIIC and IIICPN, the method of converting the interval-valued intuitionistic uncertain linguistic numbers into IIIC, and the reasoning method of IIICPN. As proofs, a subway fire accident model is adopted to confirm the feasibility of the proposed method, and comparison experiments between the IIICPN with general fuzzy Petri net and the trapezium cloud model are conducted to verify the superiority of the proposed model.
45 citations
TL;DR: In this paper, a process discovery approach implemented in PM4Py is proposed to discover an object-centric Petri net with places that correspond to object types and transitions that may consume and produce collections of objects of different types.
Abstract: Techniques to discover Petri nets from event data assume precisely one case identifier per event. These case identifiers are used to correlate events, and the resulting discovered Petri net aims to describe the life-cycle of individual cases. In reality, there is not one possible case notion, but multiple intertwined case notions. For example, events may refer to mixtures of orders, items, packages, customers, and products. A package may refer to multiple items, multiple products, one order, and one customer. Therefore, we need to assume that each event refers to a collection of objects, each having a type (instead of a single case identifier). Such object-centric event logs are closer to data in real-life information systems. From an object-centric event log, we want to discover an object-centric Petri net with places that correspond to object types and transitions that may consume and produce collections of objects of different types. Object-centric Petri nets visualize the complex relationships among objects from different types. This paper discusses a novel process discovery approach implemented in PM4Py. As will be demonstrated, it is indeed feasible to discover holistic process models that can be used to drill-down into specific viewpoints if needed.
43 citations
TL;DR: This work modeled cyberattacks using an extension of the well-known Petri net formalism, designated Petri nets with players, strategies, and costs, and demonstrated the potential of formally modeling cyberattacks and of applying reinforcement learning to improving cybersecurity.
39 citations
TL;DR: A general framework for hierarchical modeling and correctness verification of such processes is introduced and a top-level model and two kinds of bottom-level models are proposed to model such processes and collaboration patterns from different abstraction levels.
Abstract: When an emergency occurs, one of the important challenges is how to form an effective and timely response. An emergency disposal plan is usually organized as a series of emergency response processes manipulated by one emergency command center and several subordinate emergency organizations. Moreover, these subordinate organizations are usually geographically dispersed and need to collaborate with each other. In this case, designing and verifying such cross-organizational collaborative emergency response processes are complicated and time-consuming. To address this problem, we propose a hierarchical modeling and correctness verification approach. A general framework for hierarchical modeling and correctness verification of such processes is first introduced. Then, a top-level model and two kinds of bottom-level models (complex and simple bottom-level ones) are proposed to model such processes and collaboration patterns from different abstraction levels. Next, Petri net refinement operation is adopted to refine the top-level model by using its corresponding bottom-level models to obtain the refined model. Finally, the correctness of the refined model is verified based on reachability graph. A typical running case of cross-organization collaborative fire emergency response processes is given to validate our proposed method.
39 citations
TL;DR: The key idea behind the proposed approach is the online computation of a graph representing a reduced portion of the state space of a TPN system, and precisely the states that can be reached from the current one by firing only uncontrollable transitions.
Abstract: This paper deals with the enforcement of generalized mutual exclusion constraints (GMECs) on time Petri nets (TPNs) with uncontrollable transitions by restricting the firing intervals of controllable transitions. Existing approaches do not exploit the timing information and consequently the system permissiveness is limited. The key idea behind the proposed approach is the online computation of a graph representing a reduced portion of the state space of a TPN system, and precisely the states that can be reached from the current one by firing only uncontrollable transitions. Such a graph is called partial modified state class graph (PMSCG) and is derived from another graph recently presented in the literature. Based on the PMSCG, a procedure to compute a supervisory control law enforcing a GMEC on a TPN system in a maximally permissive way is presented.
38 citations
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TL;DR: In this article, the reachability semantics of Petri nets is studied in a compositional way using symmetric monoidal double functors out of pen(Petri), and two forms of semantics, operational and reachability, are given for each open Petri net.
Abstract: The reachability semantics for Petri nets can be studied using open Petri nets. For us, an “open” Petri net is one with certain places designated as inputs and outputs via a cospan of sets. We can compose open Petri nets by gluing the outputs of one to the inputs of another. Open Petri nets can be treated as morphisms of a category Open(Petri), which becomes symmetric monoidal under disjoint union. However, since the composite of open Petri nets is defined only up to isomorphism, it is better to treat them as morphisms of a symmetric monoidal double category pen(Petri). We describe two forms of semantics for open Petri nets using symmetric monoidal double functors out of pen(Petri). The first, an operational semantics, gives for each open Petri net a category whose morphisms are the processes that this net can carry out. This is done in a compositional way, so that these categories can be computed on smaller subnets and then glued together. The second, a reachability semantics, simply says which markings of the outputs can be reached from a given marking of the inputs.
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TL;DR: It is shown that it is indeed feasible to discover holistic process models that can be used to drill-down into specific viewpoints if needed, and a novel process discovery approach implemented in PM4Py is discussed.
Abstract: Techniques to discover Petri nets from event data assume precisely one case identifier per event. These case identifiers are used to correlate events, and the resulting discovered Petri net aims to describe the life-cycle of individual cases. In reality, there is not one possible case notion, but multiple intertwined case notions. For example, events may refer to mixtures of orders, items, packages, customers, and products. A package may refer to multiple items, multiple products, one order, and one customer. Therefore, we need to assume that each event refers to a collection of objects, each having a type (instead of a single case identifier). Such object-centric event logs are closer to data in real-life information systems. From an object-centric event log, we want to discover an object-centric Petri net with places that correspond to object types and transitions that may consume and produce collections of objects of different types. Object-centric Petri nets visualize the complex relationships among objects from different types. This paper discusses a novel process discovery approach implemented in PM4Py. As will be demonstrated, it is indeed feasible to discover holistic process models that can be used to drill-down into specific viewpoints if needed.
13 Sep 2020
TL;DR: This work introduces and study an extension of coloured Petri nets, called catalog-nets, providing two key features to capture this type of processes, and shows that fresh-value injection is a particularly complex feature to handle, and discusses strategies to tame it.
Abstract: During the last decade, various approaches have been put forward to integrate business processes with different types of data. Each of these approaches reflects specific demands in the whole process-data integration spectrum. One particularly important point is the capability of these approaches to flexibly accommodate processes with multiple cases that need to co-evolve. In this work, we introduce and study an extension of coloured Petri nets, called catalog-nets, providing two key features to capture this type of processes. On the one hand, net transitions are equipped with guards that simultaneously inspect the content of tokens and query facts stored in a read-only, persistent database. On the other hand, such transitions can inject data into tokens by extracting relevant values from the database or by generating genuinely fresh ones. We systematically encode catalog-nets into one of the reference frameworks for the (parameterised) verification of data and processes. We show that fresh-value injection is a particularly complex feature to handle, and discuss strategies to tame it. Finally, we discuss how catalog-nets relate to well-known formalisms in this area.
TL;DR: This paper proposes an approach to the design of a maximally permissive (optimal) controller to prevent vehicles from any collision based on Petri nets (PNs), and well addresses the challenging issues caused by indistinguishable and uncontrollable events.
Abstract: Automated guided vehicles (AGVs) are being extensively used for transportation and distribution of materials due to their high-efficiency. However, the vehicle-collision free problem is challenging since, when modeling these systems, there are indistinguishable and uncontrollable events due to the limited sensors and actuators. This paper proposes an approach to the design of a maximally permissive (optimal) controller to prevent vehicles from any collision based on Petri nets (PNs). For a typical class of AGV systems, a system modeling algorithm is presented using labeled PN, where indistinguishable events are represented by a set of transitions carrying the same label, and an uncontrollable event by an uncontrollable transition. By virtue of the PN model, the collision-free problem is formalized as a conjunction of linear constraints that are converted into admissible ones by an algorithm such that the computational overhead due to uncontrollable events is significantly reduced. In turn, a method is developed to compute the set of consistent markings for an observed sequence of labels that represent signals generated by sensors. Finally, given an observed sequence, a maximally permissive control action is computed to enforce a conjunction of admissible linear constraints based on the set of consistent markings. The approach well addresses the challenging issues caused by indistinguishable and uncontrollable events. A typical AGV system is utilized to illustrate and verify the theoretical results throughout the work.
TL;DR: This paper integrates a deadlock prevention policy with local search and develops a novel deadlock-free scheduling algorithm that supports the cooperative aspect of local search for scheduling problems strongly.
Abstract: Deadlock-free scheduling and control is critical for optimizing the performance of flexible assembly systems (FASs) Based on the Petri net models of FASs, this paper integrates a deadlock prevention policy with local search and develops a novel deadlock-free scheduling algorithm A solution of the scheduling problem is coded as a chromosome representation that is a permutation with repetition of parts By using the deadlock prevention policy, a repairing algorithm (RA) is developed to repair unfeasible chromosomes A perturbation strategy based on estimation of distribution algorithm is developed to escape from local optima Moreover, to improve population diversity, an acceptance criterion (AC) based on Pareto dominance is proposed The chromosome representation, RA, perturbation strategy, and AC together support the cooperative aspect of local search for scheduling problems strongly
TL;DR: This paper proposes a general modeling procedure for mission reliability evaluation of PMS, capable of considering the time redundancy both inner phase and between phases in relatively intuitive way and an example system under different time redundancy assumptions is analyzed to illustrate the effectiveness.
TL;DR: A new methodology for formal verification of RDECSs is proposed in order to ensure the correctness of these systems with a reduced cost (decreasing the verification time and memory occupation) and an improvement method that avoids any redundancy and cancels unnecessary calculations is developed.
Abstract: This paper deals with the formal verification of reconfigurable discrete event control systems (RDECSs) using reconfigurable timed net condition/event systems (R-TNCESs) formalism. A reconfigurable system switches from a mode to another during its working process to adapt its behavior to the related environment. By including such a feature, RDECSs become complex and their verification is often expensive in terms of computation time and memory. In this paper, a new methodology for formal verification of RDECSs is proposed in order to ensure the correctness of these systems with a reduced cost (decreasing the verification time and memory occupation). The proposed contribution includes an improved modeling and verification of RDECSs. The modeling with R-TNCESs is enriched with all reconfiguration forms, and the verification involves an improvement method that avoids any redundancy and cancels unnecessary calculations. In addition, a visual tool called Rec-AG based on the proposed methodology is developed. The performance evaluation of this paper is achieved by measuring computation time and memory for several systems and different sizes of the problem. This paper’s contribution is applied to the benchmark production system FESTO.
TL;DR: This paper develops a structurally simple Petri net deadlock controller for automated manufacturing systems (AMSs) with multiple resource requirements by designing a control place with a proper control variable for each PRT-circuit in an effective transition cover and presenting an algorithm for checking the effectiveness of transition covers, and transforming noneffective transition covers into effective ones.
Abstract: This paper focuses on the liveness analysis and deadlock control for automated manufacturing systems (AMSs) with multiple resource requirements. Such an AMS is modeled by a class of generalized Petri nets called systems of simple sequential processes with multiple resources (S3PMR). It is shown that a deadlock of the considered AMSs can be characterized by the saturation of a structural object in S3PMR, called perfect resource transition-circuit (PRT-circuit). As a consequence, an S3PMR is live if and only if no PRT-circuit is saturated at any reachable marking. To ensure the system liveness, one has to prevent all PRT-circuits from being saturated at all reachable markings. To develop a structurally simple Petri net deadlock controller, we present the concept of an effective transition cover, which is a special subset of PRT-circuits that may be saturated. Then by designing a control place with a proper control variable for each PRT-circuit in an effective transition cover, we obtain a deadlock controller for the system. The needed control variables are determined by an integer linear program. Since the number of PRT-circuits in an effective transition cover is much less than that of all PRT-circuits that need to control, our controller is of small structural size. For an AMS with saturable PRT-circuits, there exists at least a transition cover. An algorithm is presented for checking the effectiveness of transition covers, and transforming noneffective transition covers into effective ones. Finally, some examples are used to illustrate the proposed method.
TL;DR: This paper proposes a robust control algorithm in the paradigm of systems of sequential systems with shared resources, which can acquire and release resources in a multitype and multiquantity way, and is validated to be a polynomially complex robust control algorithms by the distributivity analysis.
Abstract: Up to now, the supervision and control of deadlock-free resource allocation has received considerable attention, particularly regarding their deadlock problems. To date, most solutions have supposed that allocated resources never fail. However, this is quite the opposite in reality since some resources may fail unexpectedly. A robust system should be resilient to such failures. In this paper, resources are divided into reliable ones and unreliable ones. On the basis of the deadlock avoidance algorithm which is proposed for the problem of deadlocks, we propose a robust control algorithm in the paradigm of systems of sequential systems with shared resources, which can acquire and release resources in a multitype and multiquantity way. It is validated to be a polynomially complex robust control algorithm by the distributivity analysis. Finally, experimental results show that the proposed approaches are effective as well as efficient in response to resource failures.
TL;DR: An automatic strategy for planning a team of identical robots evolving in a known environment by iterating the selection of an accepted run that satisfies the specification and the search for RMPN sequences of reachable markings that can produce desired observations.
Abstract: This research proposes an automatic strategy for planning a team of identical robots evolving in a known environment. The robots should satisfy a global task for the whole team, given in terms of a Linear Temporal Logic (LTL) formula over predefined regions of interest. A Robot Motion Petri Net (RMPN) system is used for modeling the evolution of the robotic team in the environment, bringing the advantage of a fixed topology versus the number of robots, with respect to methods based on synchronous automaton products. The algorithmic method iterates the selection of an accepted run that satisfies the specification and the search for RMPN sequences of reachable markings that can produce desired observations. A Buchi automaton witnesses the advancement towards formula fulfillment, and at the core of our methods are three Mixed Integer Linear Programming (MILP) formulations that yield firing sequences and markings of RMPN model. The cost functions of these formulations reduce the number of robot synchronizations and induce collision avoidance. Simulation examples support the computational feasibility of the proposed method.
TL;DR: In this article, it was shown that the problem of verifying strong detectability is decidable and EXPSPACE-hard for deterministic finite automata, where the decidability result holds under mild promptness assumption.
Abstract: Detectability is a basic property of dynamic systems: when it holds an observer can use the current and past values of the observed output signal produced by a system to reconstruct its current state. In this paper, we consider properties of this type in the framework of discrete-event systems modeled by labeled Petri nets and finite automata. We first study weak approximate detectability. This property implies that there exists an infinite observed output sequence of the system such that each prefix of the output sequence with length greater than a given value allows an observer to determine if the current state belongs to a given set. We prove that the problem of verifying this property is undecidable for labeled Petri nets, and PSPACE-complete for finite automata. We also consider one new concept called eventual strong detectability. The new property implies that for each possible infinite observed output sequence, there exists a value such that each prefix of the output sequence with length greater than that value allows reconstructing the current state. We prove that for labeled Petri nets, the problem of verifying eventual strong detectability is decidable and EXPSPACE-hard, where the decidability result holds under a mild promptness assumption. For finite automata, we give a polynomial-time verification algorithm for the property. In addition, we prove that strong detectability is strictly stronger than eventual strong detectability for labeled Petri nets and even for deterministic finite automata.
01 Jan 2020
TL;DR: This chapter presents a method and a prototype tool to generate secure smart contracts based on Petri Nets that allows to design and generate a secure smart contract template that can be deployed on a supported blockchain platform (e.g. Ethereum) with very little additional effort.
Abstract: Existing blockchain and smart contract development ecosystems do not support to design, develop, and verify secure smart contracts before deploying them. Recent attacks (see DAO hack [5]) on insecure smart contracts have caused a lot of financial loss—to avoid such issues in the future, we need better methods for creating secure smart contracts before deploying them in a blockchain. In this chapter, we present a method and a prototype tool to generate secure smart contracts based on Petri Nets. Our method allows to design and generate a secure smart contract template that can be deployed on a supported blockchain platform (e.g. Ethereum) with very little additional effort. One of the main advantages that our method brings into the smart contract development ecosystem is introducing a formal way to visually model, simulate, and verify business logic/workflows prior to the smart contract code generation. Modeling the smart contracts via Petri Nets helps the developers to minimize the logical errors—by verifying certain Petri Net properties such as deadlocks—during the modeling stage itself. Furthermore, our approach presents a technology-independent way to import and export the modeled use-case logic which can be translated into different smart contract language later.
TL;DR: A novel STS framework is proposed: STS with conditional-preemption matrices (STSM), which aims to solve different kinds of issues related to priority, and the optimal nonblocking supervisory control is deployed in the framework of STSM.
Abstract: State-tree structure (STS) is a powerful tool for the modeling and control of large-scale discrete-event systems (DES) whose structure is organized in a top–down hierarchy. The notorious state-explosion problem can be managed effectively in the framework of STS. Priority is an important concept and exists in a wide range of DES, such as manufacturing systems, traffic systems, and logistic (service) systems. In this article, a conditional-preemption matrix is used to describe the preemption relations among events, which can represent the priority intuitively. In order to augment STS with priority, we propose a novel STS framework: STS with conditional-preemption matrices (STSM), which aims to solve different kinds of issues related to priority. The optimal nonblocking supervisory control is deployed in the framework of STSM. Symbolic synthesis algorithms are implemented and integrated in a software tool, STSLib, which exploits binary decision diagrams as a basis for efficient computation. The developed approach is demonstrated by (a) manufacturing systems using automatic guided vehicles and (b) real-time systems.
TL;DR: By adding a control place to the Petri net models for each considered siphon, this paper develops robust deadlock controllers for the considered AMS, which ensures that the parts of all types can be processed continuously through any of its processing routes, even if one of the unreliable resources fails.
Abstract: Recently, the problem of robust control for automated manufacturing systems (AMSs) with unreliable resources receives increasing attentions. Almost all the existing related works are only concerned with the failure-prone AMSs in which each part stage utilizes only one unit of resources. While, in real-world AMS, it is often necessary to use multiple units of different resources to complete a part. This paper focuses on the robust control of such complex AMSs with a type of unreliable resources. General Petri nets are used to model all the behavior of such AMSs. By adding a control place to the Petri net models for each considered siphon, we develop robust deadlock controllers for the considered AMS. Such a robust controller ensures that the parts of all types can be processed continuously through any of its processing routes, even if one of the unreliable resources fails. Finally, some examples are used to illustrate the proposed method.
TL;DR: The paper uses the isomorphism property of the TPNs and the Markov chains for the performance analysis of the safety critical systems and the presented methodology has been validated on a Shutdown System of a Nuclear Power Plant.
TL;DR: This paper proposes a formal mapping for a real-time task model using the LNT language and describes how it is used for the integration of a formal verification phase in an AADL model-based development process, and provides a complete tool-chain for the automatic model transformation and formal verification of A ADL models.
Abstract: Formal methods have become a recommended practice in safety-critical software engineering. To be formally verified, a system should be specified with a specific formalism such as Petri nets, automata and process algebras, which requires a formal expertise and may become complex especially with large systems. In this paper, we report our experience in the formal verification of safety-critical real-time systems. We propose a formal mapping for a real-time task model using the LNT language, and we describe how it is used for the integration of a formal verification phase in an AADL model-based development process. We focus on real-time systems with event-driven tasks, asynchronous communication and preemptive fixed-priority scheduling. We provide a complete tool-chain for the automatic model transformation and formal verification of AADL models. Experimentation illustrates our results with the Flight control system and Line follower robot case studies.
TL;DR: This paper proposes a resource constrained task scheduling profit optimization algorithm (RCTSPO), which consists of clustering preprocessing, classification, profit matrix construction and optimal scheduling strategy calculation and results show that the algorithm not only achieves the maximum profit, but also performs well in terms of time, reliability and load balancing of task scheduling.
Abstract: Edge cloud is a cloud computing system built on edge infrastructure. Task scheduling optimization is the key technology to ensure the quality of service in edge cloud. However, the openness of the edge cloud environment challenges the load balancing and profit optimization of task scheduling. In this paper, we analyze the business process and optimization factors of task scheduling in edge cloud. First, we propose a resource constrained task scheduling profit optimization algorithm (RCTSPO), which consists of clustering preprocessing, classification, profit matrix construction and optimal scheduling strategy calculation. Clustering preprocessing gathers similar tasks into one class and perform a classification on the clustered tasks. Then construct the profit matrix for resource constrained task scheduling, and the optimal task scheduling strategy is obtained based on the constructed profit matrix. Second, Petri nets are used to construct the different components of edge cloud, such as resource, task, user request and virtual machine, thus forming the task scheduling model of edge cloud. Third, the properties of task scheduling model are verified by using the related theory and tools of Petri nets. Finally, several experiments are done to evaluate the proposed method, the simulation results show that the algorithm not only achieves the maximum profit, but also performs well in terms of time, reliability and load balancing of task scheduling.
TL;DR: It is shown that a behavior model represented by a set of fUML‐compliant modeling elements in UML/SysML activity diagrams can be transformed into an equivalent PN, so that the analysis capability of PN can be applied.
TL;DR: This is the first paper to use TPNs to model a variable phase traffic light control system and identify its accident scenarios for the purpose of their complete avoidance and proposes a new control strategy to eliminate the traffic jam propagation by preventing the traffic flow heading in the direction of an accident.
Abstract: Cell transmission model (CTM) is useful for evaluating the performance of urban traffic networks due to its mathematical formalism. This paper explores the application of CTM to develop control strategies for dispersion accident-induced traffic jams and evaluates the efficiency of these strategies. On the other hand, Timed Petri nets (TPNs) perform in discrete event systems because they provide a balance between modeling power and analyzability. This paper focuses on using the developed TPNs to model variable traffic light control systems. One advantage of the proposed methods is that the traffic light behavior is clearly represented in terms of conditions and events, which result in changes in the pre-emption phase. Moreover, this paper also proposes a new control strategy to eliminate the traffic jam propagation by preventing the traffic flow heading in the direction of an accident. The analysis is performed to demonstrate how the models enforce the phase of traffic transitions by a reachability graph with time information. The liveness and reversibility of the proposed model are verified. To the best of our knowledge, this is the first paper to use TPNs to model a variable phase traffic light control system and identify its accident scenarios for the purpose of their complete avoidance. This helps the latest advanced technology in traffic safety related to the intersection of roadways.
TL;DR: A multilevel smart contract modeling solution to analyze the security of contract is proposed, improving the program logic rules for bytecode and applying the Hoare condition to create a Colored Petri Net (CPN) model.
Abstract: Smart contracts increasingly cause attention for its ability to widen blockchain's application scope. However, the security of contracts is vital to its wide deployment. In this article, we propose a multilevel smart contract modeling solution to analyze the security of contract. We improve the program logic rules for bytecode and apply the Hoare condition to create a Colored Petri Net (CPN) model. The model detection method provided by the CPN tools can show the full-state space and the wrong execution path, which help us analyze the security of the contract from several perspectives. The example shows that the counter-example path given by the contract model is accord with our expected results based on code analysis, proving the correctness of the solution. In addition, we design a highly automated modeling method, introducing custom call libraries and a path derivation algorithm based on backtracking, which improves the efficiency and pertinence of the dynamic simulation of CPN models.