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Owing to increasingly important drivers for change, such as automation, digitisation, and dynamic demand patterns, simulation models of production systems become outdated rapidly. At the same time, building simulation models often requires much time, cost, and expertise, especially when dealing with complex job shop production systems. To address these challenges, an automated simulation model generation (ASMG) framework for material flow simulation of production systems is presented. This framework contains multiple approaches to infer routeing, control and temporal aspects from event-based data. To achieve this, methods from process mining (PM) and machine learning (ML) are applied. Additionally, the suitability of Coloured Petri Nets (CPNs) to serve as conceptual and operational simulation models is examined. The inferred simulation models have high validity when compared to the real system concerning the KPIs machine utilisation, throughput, and work in process. It is shown, that most model elements can be inferred very well, in particular process routes, processing times, and resource selection rules. This proof of concept serves as a foundation for research on detection approaches inferring further model elements such as setup times accurately. [ABSTRACT FROM AUTHOR]

The transport sector is responsible for about 60% of emissions in the atmosphere due to the exhaust-polluting gases of internal combustion engine (ICE) vehicles. An effective solution to this issue is the electrification of the transport means, which can significantly reduce pollution, especially in urban areas. Apart from the necessary technological advancements that must improve the battery performances, the diffusion of electric vehicles (EVs) must be further supported and facilitated by new dedicated services and tools for electric vehicle users and operators aiming at improving the travel and charging experience. To this goal, this paper proposes new models based on Timed Colored Petri Nets (TCPN) to simulate and manage the charge demand of the EV fleet. At first, the proposed tool must take into account the charging requests from different EV drivers with different charging need located in different geographical areas. This is possible by knowing input data such as EV current location, battery data, charge points (CPs) availability, and compatibility. In particular, EV drivers are simulated when finding and booking the preferred charge option according to the available infrastructure in the area of interest and the CPs tariff and power rate. The proposed TCPN is designed to model the multi-user charging demand in specific geographic areas, and it is evaluated in several scenarios of a case study to measure its performance in serving multiple EV users. [ABSTRACT FROM AUTHOR]

Traffic flow at urban intersections varies randomly during the day. It depends on several dynamic factors and requires efficient regulation and flexible control strategies in particular for traffic light regulation. The proposed strategy allows managing the green light time autonomously. The dynamic behavior of traffic signals at intersections can be seen as a discrete event system. Through this paper, a modular Timed Synchronized Petri Net (TSPN) model is developed using a real-time adaptive control strategy of urban signalized intersections. The control is shared between two communicant actors. The slaves (TSPN modules) control the traffic signal displays, phases transitions, and model traffic flow fluctuations. The master (controller) decides the next phase that should be serviced and calculates its variable green light time. Attributable to their modularity, the developed models reduce complexity, and, more importantly, they are able to be adapted easily to any real intersection. Furthermore, various traffic signals control strategies could be implemented using these models. However, some interesting properties of the system are checked, and some simulations are performed and analyzed in order to validate the proposed control approach. [ABSTRACT FROM AUTHOR]

The exploration of pathways and alternative pathways that have a specific function is of interest in numerous chemical contexts. A framework for specifying and searching for pathways has previously been developed, but a focus on which of the many pathway solutions are realizable, or can be made realizable, is missing. Realizable here means that there actually exists some sequencing of the reactions of the pathway that will execute the pathway. We present a method for analyzing the realizability of pathways based on the reachability question in Petri nets. For realizable pathways, our method also provides a certificate encoding an order of the reactions, which realizes the pathway. We present two extended notions of realizability of pathways, one of which is related to the concept of network catalysts. We exemplify our findings on the pentose phosphate pathway. Furthermore, we discuss the relevance of our concepts for elucidating the choices often implicitly made when depicting pathways. Lastly, we lay the foundation for the mathematical theory of realizability. [ABSTRACT FROM AUTHOR]

NFV (Network Function Virtualization) is an innovative paradigm that seeks to improve the flexibility and efficiency of network services. NFV focuses on virtualizing network functions, allowing them to be executed on generic hardware, which decouples software and hardware and allows for more agile and scalable implementations. Through NFV, the concept of SFC (Service Function Chain) emerges, which consists of a sequence of VNFs (Virtual Network Functions), such as gateways, firewalls, and routers, arranged in an orderly manner. A critical challenge faced by SFC is its sensitivity to latency: delay increases as the chain of VNFs lengthens, which can compromise the quality of service. Minimizing this latency is crucial to ensure the efficiency of SFC systems. However, testing different SFC architectures in real environments is costly. As a solution, this study proposes using Stochastic Petri Nets (SPNs) for a performance evaluation of SFC architectures. The developed SPN model allows for analyzing different configurations of VNFs in sequential, parallel, and hybrid architectures. Four case studies were carried out exploring the behavior of the proposed model under different analyses and scenarios. The results obtained were validated through simulations in GNS3 (Graphical Network Simulator-3). The data demonstrate that changes in the SFC architecture can result in significant performance improvements and latency reduction. [ABSTRACT FROM AUTHOR]

In the era of Industry 4.0 and individualized mass customization, the demand for adaptable manufacturing systems is paramount. Therefore, assembly plans used in such systems must also allow a high degree of flexibility to adapt to changing requirements and conditions. At the same time, they must still guarantee the successful execution of the assembly process. In this paper, we present a novel approach to modeling assembly plans in the context of an ongoing, larger project in which we intend to implement flexible manufacturing in a real production cell. In our assembly plans, we specifically emphasize flexibility regarding the order of assembly steps, the allocation of appropriate teams of robots to execute these steps with applicable parts, and the ability to respond to failures in the system. We present a comprehensible modeling of flexible assembly plans, accompanied by the semantics of Petri nets, illustrated by example, and comparatively evaluated against other approaches. [ABSTRACT FROM AUTHOR]

Electric vertical takeoff and landing (eVTOL) technology can improve connectivity while minimizing reliance on traditional ground-based transportation systems. However, the rapid growth in eVTOL adoption brings challenges in managing landing pad operations and scheduling routes effectively. This study aims to analyze eVTOL landing operations and provide a framework for evaluating system performance under different configurations. Key objectives include (i) identifying bottlenecks in landing pad operations, (ii) proposing improvements to enhance scalability and efficiency through multi-route and multi-pad configurations, and (iii) assessing the impact of operational parameters, such as increased horizontal speed, on overall performance. A simulation analysis was conducted using an original model developed with colored, timed Petri net technology. This methodology aligns with the principles of probabilistic modeling and queuing systems. The experiments provided a comprehensive analysis of the factors influencing the scalability and efficiency of eVTOL operations. A key finding across all experiments is the identification of the "Landing Confirmed—Move to V" as a consistent bottleneck stage. While increasing routes and pads significantly alleviates arrival delays, it does not address identified bottlenecks, which require innovative solutions such as route optimization or speed enhancements. The results underscore the importance of a robust and adaptable framework to support the increasing demand for eVTOL traffic. Urban planners and policymakers can utilize these findings to prioritize the development of vertiports capable of supporting this expanding mode of transportation. The scalability demonstrated in this study validates the feasibility of eVTOL systems as a viable solution for urban mobility. [ABSTRACT FROM AUTHOR]

This article presents the design and implementation of an API that delivers real-time promotional notifications to mobile devices based on their proximity to shopping centers, calculated using the Haversine formula. Developed in Laravel, the API determines whether a mobile device is within a 600 m radius of any registered shopping center, such as Soriana, GranD, and HEB, and sends the relevant promotional information. The system uses Petri nets to model asynchronous behavior, enabling efficient concurrency management between the mobile application and the API. This structure ensures optimized message delivery, preventing communication collisions and delays. The mobile application, developed in Kotlin, integrates geolocation services to capture and update the user's location in real time. The results indicate an improvement in response time and proximity detection accuracy, highlighting the effectiveness of the Petri net model for systems requiring concurrent interaction. The combination of Laravel, Kotlin, and formal modeling with Petri nets proves to be an effective and scalable solution for proximity-based mobile applications. [ABSTRACT FROM AUTHOR]

The study of real discrete event systems requires the use of models to cope with complexity and large scale. The only way to understand and analyse their behaviour prior to implementation is, in practice, through distributed simulation. Although it is a widely studied discipline, the difficulty of developing efficient distributed simulation code remains a challenge. The use of model driven engineering approaches allows a smooth way from informal specifications to executable code showing traces of the system behaviour. Formal models allow to conduct the phases of this engineering process, and in this work, the formalism is Petri nets. In the simulation literature, Petri nets have been shown to be particularly suitable for modelling and simulation of discrete event systems. This article reviews the role of Petri nets as the core formalism to support a model‐driven engineering approach for the execution of large scale models using distributed simulation. It deals with different aspects related to the Petri net‐based languages used at different stages of the modelling and simulation process, from conceptual modelling of complex systems to the generation of code for executing simulations of Petri net‐based models. After the review, the article proposes an efficient representation of Petri net‐based models. It is analysed from the perspective of the essential properties required for distributed simulation, and was found to provide efficient execution, scalability and dynamic configuration. The article highlights the importance of considering modelling constraints in order to guarantee good properties such as liveness and structural boundedness of Petri net components for the execution of large‐scale Petri net models. The Petri net‐based methodology is illustrated from the perspective of the impact of the formalism to help developing well‐formed models and efficient code for distributed simulation. [ABSTRACT FROM AUTHOR]

This paper deals with a "digital twin" (DT) approach for processing, reprocessing, and scrapping (P/R/S) technology running on a modular production system (MPS) assisted by a mobile cyber–physical robotic system (MCPRS). The main hardware architecture consists of four line-shaped workstations (WSs), a wheeled mobile robot (WMR) equipped with a robotic manipulator (RM) and a mobile visual servoing system (MVSS) mounted on the end effector. The system architecture integrates a hierarchical control system where each of the four WSs, in the MPS, is controlled by a Programable Logic Controller (PLC), all connected via Profibus DP to a central PLC. In addition to the connection via Profibus of the four PLCs, related to the WSs, to the main PLC, there are also the connections of other devices to the local networks, LAN Profinet and LAN Ethernet. There are the connections to the Internet, Cloud and Virtual Private Network (VPN) via WAN Ethernet by open platform communication unified architecture (OPC-UA). The overall system follows a DT approach that enables task planning through augmented reality (AR) and uses virtual reality (VR) for visualization through Synchronized Hybrid Petri Net (SHPN) simulation. Timed Petri Nets (TPNs) are used to control the processes within the MPS's workstations. Continuous Petri Nets (CPNs) handle the movement of the MCPRS. Task planning in AR enables users to interact with the system in real time using AR technology to visualize and plan tasks. SHPN in VR is a combination of TPNs and CPNs used in the virtual representation of the system to synchronize tasks between the MPS and MCPRS. The workpiece (WP) visits stations successively as it is moved along the line for processing. If the processed WP does not pass the quality test, it is taken from the last WS and is transported, by MCPRS, to the first WS where it will be considered for reprocessing or scrapping. [ABSTRACT FROM AUTHOR]

This paper introduces a novel algorithm for the efficient verification of a Petri net-based concurrent control system. The proposed method is based on the computation of transition invariant coverage to detect possible errors in the modelled system. Transition invariants play a crucial role in ensuring the correctness and reliability of such systems; however, existing methods often struggle with high computational demand, especially in the case of large and complex systems. The proposed approach addresses this challenge by performing a fast polynomial-time analysis to identify uncovered transitions, thereby streamlining the verification process. The effectiveness and efficiency of the proposed technique is verified experimentally with a set of 386 test modules (benchmarks) and compared against two well-known established methods: the classical method proposed by Martínez–Silva (as a reference algorithm) and PIPE (Platform Independent Petri Net Editor) tool. The results of the experiments confirm high performance of the presented algorithm, which was able to compute results for all the tested cases. In contrast, both the reference algorithm as well as the PIPE tool failed to deliver results for all examined models within one hour. The proposed algorithm is especially useful in early design stages, offering system designers timely insights into potential issues. [ABSTRACT FROM AUTHOR]

Fault diagnosis and maximum fault-free execution are essential for the development and operation of computer-integrated systems covering aircraft systems, power grid systems, production processes, etc. This paper focuses on the problem of fault diagnosis and maximum fault-free enforcement of systems modeled by labelled Petri nets. Given a system modeled by a labelled Petri net that may enter deadlocks, an extended basis reachability graph that contains sufficient information to characterize deadlocks is used to compress the state space and verify the diagnosability for the considered system. Furthermore, the proposed graph offers sufficient and necessary conditions for fault-free enforcement and deadlock-free enforcement. Finally, a lock-free event set and a supervisor are designed for a system such that any possible fault or dead behaviour is prohibited in the controlled system. [ABSTRACT FROM AUTHOR]

This paper proposes a novel methodology for the design of dual-stack IP routing protocols focused on neighborships and routing messages transport. The first part describes currently used dual-stack IP routing protocols, their history, and key features. The description of four identified combinations based on a number of neighbor sessions and protocol used for the transport of routing messages is presented afterward. These combinations are introduced as Protocol Integration Solution Classes (PISCs) in this paper. Colored Petri nets (CPNs) are selected as a formal method to create a model of each PISC. The following parts deal with a detailed description and analysis of the created Protocol Integration Solution Class models, which are also verified and compared with each other. Based on the comparison of each PISC model simulation step, the PISC 2 class is selected as the most efficient one. The last part of the paper formulates recommendations for the dual-stack IP routing protocol design based on the results presented in this paper. [ABSTRACT FROM AUTHOR]

In automated manufacturing systems (AMSs), because of unpredictable failures, resources can lose functions such that the deadlock control methods, in existence, are invalidated. In this paper, a robust deadlock control approach is proposed for AMSs with multiple unreliable resources. The considered AMSs modelled by Petri nets (PNs) allow to acquire different types of resources at each processing stage. In order to visualise the fact that resource failures occur in AMSs, recovery subnets are designed for the modelling AMSs to depict the failures and recoveries of resources. Based on a siphon detection method performed by a set of integer linear programming formulations, a control specification is proposed. Control places (monitors) with their control variables are designed for the detected unmarked siphons at a marking to guarantee that they are always marked even if some unreliable resources break down. Iteratively, all unmarked siphons are detected and controlled. Therefore, a robust deadlock supervisor is synthesised to ensure the controlled system's liveness no matter there exist resource failures or not. The theoretical analyses and proof are given to verify the correctness of the proposed method. Finally, the comparative studies are presented to expound the proposed method's effectiveness and efficiency. [ABSTRACT FROM AUTHOR]

Abstract Along with the development of industrial and distributed systems, security concerns have also emerged in industrial communication protocols. PTP, Precision Time Protocol, is one of the most precise time synchronisation protocols for industrial devices. It ensures real‐time activity of the industrial control systems with precision equal to microseconds. In order to address the actual or potential security issues of PTP, this article firstly describes attack models applicable to PTP and then focuses on applying Coloured Petri Net to formally analyse the attack detection methods and also model PTP. The alignment of simulation results with the model and the considered assumptions show the suitability and accuracy of the proposed model.

Abstract This paper addresses the problem of optimal sensor selection for ensuring diagnosability of discrete event systems. Given a nondiagnosable discrete event system modeled with labeled Petri nets, a new labeling function can be designed to enforce the system to be diagnosable. An ad‐hoc parallel composition of non‐deterministic finite automata (derived from the original labeled Petri net model) that are observed at multiple observation sites is employed. In order to optimize a given labeling function as well as a sensor selection, an integer linear programming problem is formulated to associate numerical sensor costs with transition relabelings. In a multi‐fault system, this method can determine the type of faults that occur and the fault sequences pertaining to this fault type if multiple faults occur. Examples are presented to demonstrate the proposed method.

Purpose: The primary purpose of this paper is to use a process mining method on collected and appropriately prepared event logs from the MES class system of the entity under study. Design/methodology/approach: With the classical process mining approach using the XES standard, the Alpha algorithm and Petri nets, event logs of the manufacturing process were analysed. To perform the analysis, 379,341 rows of data were extracted from the MES system, representing 7194 instances and 76 different activities. Findings: a key result of the presented research is the conclusion regarding the quality of the data generated by the controllers. Timestamps for events in the MES system may need to be corrected. Research limitations/implications: The paper presents a case study for a specific set of controllers and an MES system. For this particular configuration, additional mechanisms are required to synchronise time stamps from one location (e.g. an NTP server). The results may be different for a different hardware and software configuration of the MES system. Practical implications: The result of the research carried out in this paper also leads to conclusions of a practical nature. Incorrect synchronisation of times makes it impossible to control and analyse the process as a whole, even when the whole process is working correctly as an assembly of individual operations. The guidelines developed were passed on to those responsible for the operation of the MES system. Originality/value: In the literature, various case studies can be found for process mining including event logs of ERP systems of others. The authors did not find similar studies for MES systems. In particular, the classical approach for log preparation requires awareness of potential time synchronisation problems. [ABSTRACT FROM AUTHOR]

Intrusion Detection Systems (IDSs) are a crucial component of modern corporate firewalls. The ability of IDS to identify malicious traffic is a powerful tool to prevent potential attacks and keep a corporate network secure. In this context, Machine Learning (ML)-based methods have proven to be very effective for attack identification. However, traditional approaches are not always applicable in a real-time environment as they do not integrate concrete traffic management after a malicious packet pattern has been identified. In this paper, a novel combined approach to both identify and discard potential malicious traffic in a real-time fashion is proposed. In detail, a Long Short-Term Memory (LSTM) supervised artificial neural network model is provided in which consecutive packet groups are considered as they flow through the corporate network. Moreover, the whole IDS architecture is modeled by a Petri Net (PN) that either blocks or allows packet flow throughout the network based on the LSTM model output. The novel hybrid approach combining LSTM with Petri Nets achieves a 99.71% detection accuracy—a notable improvement over traditional LSTM-only methods, which averaged around 97%. The LSTM–Petri Net approach is an innovative solution combining machine learning with formal network modeling for enhanced threat detection, offering improved accuracy and real-time adaptability to meet the rapid security needs of virtual environments and CPS. Moreover, the approach emphasizes the innovative role of the Intrusion Detection System (IDS) and Intrusion Prevention System (IPS) as a form of "virtual sensing technology" applied to advanced network security. An extensive case study with promising results is provided by training the model with the popular IDS 2018 dataset. [ABSTRACT FROM AUTHOR]

Ventricular assist devices (VADs) are designed to provide sufficient blood flow to patients with severe heart failure. Once implanted, the patient becomes dependent on the VAD, making it essential to prevent situations that could harm the patient while receiving circulatory support. VADs are classified as critical systems (CS), and adverse events (AEs) can lead to serious consequences, including hospitalization or even death. At present, patient care is provided through in-person consultations, with incidents reported via medical device reports (MDRs) to the Food and Drug Administration (FDA). However, there is no real-time monitoring of AEs or oversight of these events. In response to this gap, a system for supervising critical adverse processes in patients with implanted VADs (SCVAD) is proposed, based on horizontally and vertically integrated architecture. This system aims to address the complexity of AEs by considering multiple domains of operation: the device, the patient, and the medical team, as well as the interactions between these entities. In this context, the formalism of Petri nets (PN) is used to develop models that represent adverse processes based on the actions recommended by the medical team. These models allow for the mapping of events with the potential to cause harm to the patient. Therefore, the medical team will be able to monitor adverse processes, as the models in interpreted PN can be isomorphically transcribed into computable algorithms that can be processed on compatible devices, enabling the tracking of complications caused by adverse processes. [ABSTRACT FROM AUTHOR]

This study addresses the problem of attack identification in discrete event systems modeled with Petri nets, focusing specifically on sensor attacks that mislead observers to making incorrect decisions. Insertion attacks are one of the sensor attacks that are considered in this work. First, we formulate a novel observation structure to systematically model insertion attacks within the Petri net framework. Second, by generating an extended reachability graph that incorporates the observation structure, we can find a special class of markings whose components can have negative markings. Third, an observation place is computed by formulating an integer linear programming problem, enabling precise detection of attack occurrences. The occurrence of an attack can be identified by the number of tokens in the designed observation place. Finally, examples are provided to verify the proposed approach. Comparative analysis with existing techniques demonstrates that the reported approach offers enhanced detection accuracy and robustness, making it a significant advancement in the field of secure discrete event systems. [ABSTRACT FROM AUTHOR]

The article "Viscous Marangoni migration of an inviscid bubble by surfactant spreading: an exactly solvable model" in the Journal of Fluid Mechanics explores the movement of an inviscid bubble in a viscous fluid due to surfactant spreading. The study analyzes the bubble's speed and displacement based on initial surfactant distribution, identifying a weak finite-time singularity. An exact solution is derived for infinite surface Péclet number using the method of characteristics, with special initial conditions leading to explicit solutions in terms of the Lambert W-function. The research delves into the viscous Marangoni migration of a two-dimensional bubble, offering insights into the dynamics of Marangoni flows and potential advancements in the field. [Extracted from the article]

The NC-Link protocol, as an integrated communication protocol in the Computerized Numerical Control (CNC) machine tool industry, has drawn significant attention regarding its security since its inception. Although there have been studies proposing improvements to address security issues related to key management and message transmission, systematic security analysis of the protocol remains relatively weak. To better investigate and enhance the security of the NC-Link protocol, our research introduces a formal modeling and analysis method based on Colored Petri Nets (CPN). By establishing a CPN model of the protocol, we analyze the security issues present during communication and propose improvement measures for verification and analysis. First, we developed a CPN model for the NC-Link protocol and verified the model's feasibility through simulation analysis. Subsequently, we introduced an attacker model to analyze the protocol's authentication interaction process, revealing security issues, such as authentication vulnerabilities and key management flaws. Finally, we proposed an improved scheme addressing these issues and conducted a security validation and cost analysis of this scheme. The results show that the improved protocol reduces the computational overhead by 75% during the connection and interaction phases. This indicates that the improved protocol can achieve interactions at a faster speed while maintaining higher security and reliability. The implementation of this scheme provides new reference ideas for related research. [ABSTRACT FROM AUTHOR]

Simulation is a helpful preliminary step for implementing a patient workflow management system. Simulation is based on the process model (the clinical practice guideline) and the organization model (human and technological resources), permitting the detection of blockages in the care delivery organization and finding the optimal resource allocation. Our study uses stochastic Petri net (SPN) to illustrate part of the medical practice within a stroke unit. In particular, we modeled the medical activities following the guidelines for the ischemic stroke treatment adopted by the Thai Nguyen National Hospital Stroke Unit. Several parameters have been estimated using a database of about 100 ischemic stroke patients collected and eliciting knowledge from the neurologists. This is the first time we have applied SPN to model and analyze system performance for emergency stroke patients using the SPN model. We can apply it to any medical examination and treatment system if we need to survey the system's capacity. Thereby detecting barriers or limitations of the system to provide solutions to overcome and improve the system's efficiency. [ABSTRACT FROM AUTHOR]

Studies in the area of mobile robotics have advanced in recent years, mainly due to the evolution of technology and the growing need for automated and dynamic solutions in sectors such as industry, transport, and agriculture. These devices are complex and the ideal method for localizing, mapping, and navigating autonomous mobile robots changes depending on the application. Thus, the general objective of this work is to propose a simultaneous localization and mapping method for autonomous mobile robots in indoor environments, using computer vision (CV) and Petri net (PN). A landmark was placed next to each door in the analyzed region and images were acquired as the rooms in the environment were explored. The algorithm processes the images to count and identify the doors. A transition is created in the PN for each door found and the rooms connected by these doors are represented by the places in the PN. Then, one of the doors is crossed, new images are obtained and the process is repeated until all rooms are explored. The algorithm generates a PN, which can be represented by an image file (.png) and a file with the extension.pnml. The results compare the layout of four environments with the respective generated PNs. Furthermore, six evaluation criteria are proposed for validating Petri nets as a topological map of environments. It is concluded that using PN for this purpose presents originality and potential innovation, being a SLAM technique for indoor environments, which demands low computational cost. [ABSTRACT FROM AUTHOR]

A dynamical system is considered such that, in this system, particles move on a toroidal lattice of the dimension N1×N2$$ {N}_1\times {N}_2 $$ according to a version of the rule of particle movement in Biham–Middleton–Levine traffic model. We introduce a stochastic case with direction choice for particles. Particles of the first type move along rows, and the particles of the second type move along columns. The goal is to find conditions of self‐organization system for any lattice dimension. We have proved that the BML model as a dynamical system is a special case of Buslaev nets. This equivalence allows us to use of Buslaev net analysis techniques to investigate the BML model. In Buslaev nets conception, the self‐organization property of the system corresponds to the existence of velocity single point spectrum equal to 1. In the paper, we consider the model version when one notable aspect is that a particle may change its type. Exactly, we assume a constant probability q$$ q $$ that a particle changes type at each step. In the case where q=0$$ q=0 $$, the system corresponds to the classical version of the BML model. We define a state of the system where all particles continue to move indefinitely, in both the present and the future, as a state of free movement. A sufficient condition for the system to result in a state of free movement from any initial state (condition for self‐organization) has been found. This condition is that the number of particles be not greater than half the greatest common divisor of the numbers N1,N2,...,Nn$$ {N}_1,{N}_2,\dots, {N}_n $$. It has been proved that, if n=2$$ n=2 $$, and whether 0

Cybersecurity is an urgent concern. Cybersecurity simulation is an important part of the response to it. This article describes a research program consisting of several interconnected cybersecurity simulation research projects. Cyberattacks are modeled using Petri nets extended with features designed for modeling cyberattacks, including representations of the attacker's and defender's strategies, their actions, and their actions' cost. A database of known attack patterns is automatically processed to generate cyberattack component models, one for each attack pattern. The models are verified and validated using multiple application-relevant methods that consider both Petri nets' theoretical properties and cyberattacks' practical characteristics. Because the source attack pattern database is attacker-centric, the cyberattack component models are enhanced to include defender actions and responses, as well as representations of normal user activities on the computer system being attacked. Cyberattack component models stored in a repository are selected and composed into complete models of target computer systems. Metadata associated with each model guides the selection and composition. The cyberattack models are executed to simulate cyberattacks. Multiple simulation iterations are used to train reinforcement learning algorithms that automatically learn improved attacker or defender strategies. [ABSTRACT FROM AUTHOR]

Opacity is an important system property that is particularly relevant in the context of system security and privacy. A system is considered opaque if the predefined secret behavior of the system is not leaked to an external intruder. In this work, the opacity property is studied in the framework of labeled Petri nets (LPNs). The secret in an LPN system is characterized by a subset of reachable markings. Firstly, an opacity basis reachability graph (OBRG) containing opacity information of the system is developed to denote a system's reachability set without computing all reachable states. Then the observer of the OBRG is computed, based on which a necessary and sufficient condition is derived to verify the opacity of the LPN system. Finally, given an LPN that does not satisfy the opacity, a maximally permissive supervisor is introduced to guarantee that the controlled system is opaque. [ABSTRACT FROM AUTHOR]

Hyperledger Fabric is a platform for permissioned blockchain networks that enables secure and auditable distributed data storage for enterprise applications. There is a growing interest in applications based on this platform, but its use requires the configuration of different blockchain parameters. Various configurations impact the system's non-functional qualities, especially performance and cost. In this article, we propose a Stochastic Petri Net to model the performance of the Hyperledger Fabric platform with different blockchain parameters, computer capacity, and transaction rates. We also present a set of case studies to demonstrate the feasibility of the proposed model. This model serves as a practical guide to help administrators of permissioned blockchain networks find the best performance for their applications. The proposed model allowed us to identify the block size that leads to a high mean response time (ranging from 1 to 25 seconds) caused by a change in the arrival rate. [ABSTRACT FROM AUTHOR]

Verifying industrial robotic systems is a complex task because those systems are distributed and solely defined by their implementation instead of models of the system to be verified. Some technologies mitigate parts of this problem, e.g., robotic middleware such as the Robotic Operating System (ROS) or concrete solutions such as automata-based specification of robot behavior. However, they all lack the required modeling depth to describe the structure, behavior, and communication of the system. We introduce an improved version of our previous model-driven approach based on Petri nets, integrating these three aspects of ROS-based systems. Using a formal modeling language enables verification of the described system and the generation of complete system parts in the form of ROS nodes. This reduces testing effort because the specification of component workflows and interfaces remains formally proven, while only changed implementations have to be revalidated. We extended our previous approach with novel model transformations, which considerably improved our approach's performance and memory requirements. We evaluate our approach in a case study involving multiple industrial robotic arms and show that the structure of and communication between ROS nodes can be described and verified. [ABSTRACT FROM AUTHOR]