Hierarchical Colored Petri Nets Research Articles

Modeling and safety analysis for collaborative safety-critical systems using hierarchical colored Petri nets

ContextCollaborative systems enable multiple independent systems to work together towards a common goal. These systems can include both human-system and system-system interactions and can be found in a variety of settings, including smart manufacturing, smart transportation, and healthcare. Safety is an important consideration for collaborative systems because one system's failure can significantly impact the overall system performance and adversely affect other systems, humans or the environment. GoalFail-safe mechanisms for safety-critical systems are designed to bring the system to a safe state in case of a failure in the sensors or actuators. However, a collaborative safety-critical system must do better and be safe-operational, for e.g., a failure of one of the members in a platoon of vehicles in the middle of a highway is not acceptable. Thus, failures must be compensated, and compliance with safety constraints must be ensured even under faults or failures of constituent systems. MethodIn this paper, we model and analyze safety for collaborative safety-critical systems using hierarchical Coloured Petri nets (CPN). We used an automated Human Rescue Robot System (HRRS) as a case study, modeled it using hierarchical CPN, and injected some specified failures to check and confirm the safe behavior in case of unexpected scenarios. ResultsThe system behavior was observed after injecting three types of failures in constituent systems, and then safety mechanisms were applied to mitigate the effect of these failures. After applying safety mechanisms, the HRRS system's overall behavior was again observed both in terms of verification and validation, and the simulated results show that all the identified failures were mitigated and HRRS completed its mission. ConclusionIt was found that the approach based on formal methods (CPN modeling) can be used for the safety analysis, modeling, validation, and verification of collaborative safety-critical systems like HRRS. The hierarchical CPN provides a rigorous way of modeling to implement complex collaborative systems.

Formal Analysis of Reentrancy Vulnerabilities in Smart Contract Based on CPN

A smart contract is a special form of computer program that runs on a blockchain and provides a new way to implement financial and business transactions in a conflict-free and transparent environment. In blockchain systems such as Ethereum, smart contracts can handle and autonomously transfer assets of considerable value to other parties. Hence, it is particularly important to ensure that smart contracts function as intended since bugs or vulnerabilities may lead, and indeed have led, to substantial economic losses and erosion of trust for blockchain. While a number of approaches and tools have been developed to find vulnerabilities, formal methods present the highest level of confidence in the security of smart contracts. In this paper, we propose a formal solution to model a smart contract based on colored Petri nets (CPNs). Herein, we focus on the most common type of security bugs in smart contract, i.e., reentrancy bugs, which led to a serious financial loss of around USD 34 million for the Cream Finance project in 2021. We present a hierarchical CPN modelling method to analyze potential security vulnerabilities at the contract’s source code level. Then, modeling analysis methods such as correlation matrix, state space report and state space graph generated via CPN Tools simulation are exploited for formal analysis of smart contracts. The example shows the full state space and wrong path in accordance with our expected results. Finally, the conclusion was verified on the Ethereum network based on the Remix platform.

Urban Logistics Services Supply Chain Process Modelling Based on the Underground Logistics System via the Hierarchical Colored Petri Net

The implementation of the urban underground logistics system (ULS) can effectively mitigate the contradiction between the surging logistics demand and the increased negativity of urban logistics. The widespread implementation of ULS still suffers from a lack of research into its operation in the marketplace, although the research on ULS system technology and network design appears to be sufficient. A new supply chain for logistics service based on ULS (ULS-SSC) was proposed, as ULS embedded in the urban logistics system could lead to the evolution of the role of supply chain participants. This article analyzed the organizational structure and operation characteristics of ULS-SSC and designed a top-down ULS-SSC operation process model based on the designed functional structure and subsystems relationship using the hierarchical colored Petri net (HCPN). The simulation results show that the integrated information management platform based on ULS can integrate urban logistics service supply chain resources and operate effectively under the two main service modes designed. The high-time delay intermediate links can be upgraded by system optimization, and the links with initial pickup and terminal distribution can be improved through outsourcing and supply chain collaboration. The findings provide new insights into the feasibility of the operation of ULS in the market and help stimulate the implementation of ULS.

Formal Verification and Implementation of an E-Voting System

The organization of free, democratic, and transparent elections requires on the one hand an independent national electoral authority that manages all the stages of the electoral process and on the other hand the use of new information and communication techniques to manage the election process. E-voting offers the ability to vote online anytime and from anywhere using a computer, smartphone, or tablet. In addition, it saves time and reduces costs and effort spent in the process. However, the security of e-voting applications deployed on the internet is a difficult task due to the increasing number of cyber-attacks and application vulnerabilities. On the other hand, blockchain technology is an emerging technology with a strong cryptographic foundation. In this paper, the authors propose a new secure e-voting system based on Ethereum blockchain. In addition, they propose a hierarchical coloured petri net (HCPN) model for their e-voting system using CPN Tools. They verify by means of simulation techniques and state space analysis important properties such as absence of deadlocks and livelocks.

Modelling and Simulation of Patient Flow in the Emergency Department During the COVID-19 Pandemic Using Hierarchical Coloured Petri Net

The emergency department (ED) faces great challenges during the corona pandemic, which has greatly affected the course of work, as the medical staff works to maintain the quality of service and more guarantee the health of patients and staff. With the rapid spread of the coronavirus, ED has become the focus of attention of many researchers, where most of them focused on reducing waiting time and the duration of the patient's length of stay (LOS) through the restructuring of ED. In this study, the authors propose a simulation model using the hierarchical coloured-petri nets (CP-Nets). Several improvement scenarios have been suggested in order to arrive at the optimal solution. Scenarios were compared and solutions were presented to decision makers. This study was conducted at the Hassani Abdelkader Hospital in Sidi Bel Abbes. The authors obtained a model that could be generalized to other hospitals.

Qualitative and Quantitative Safety Evaluation of Train Control Systems (CTCS) With Stochastic Colored Petri Nets

Currently qualitative as well as quantitative safety analysis of railway systems are usually conducted through Fault Tree Analysis (FTA) and Event Tree Analysis (ETA). FTA and ETA display the causalities and consequences of hazards or accidents by means of linear event sequences, which makes it difficult to incorporate non-linear relationships such as feedback. The repair of failure system components is not considered in traditional FTA and ETA. Moreover, quantitative safety evaluation by FTA and ETA requires that failure events should be statistically independent. Considering these issues, we propose an approach of conducting qualitative as well as quantitative safety evaluation of the CTCS-3 with stochastic Coloured Petri Nets (CPNs). The hierarchical CPN model of the CTCS-3 takes the scenarios, movement of trains, the failure and repair of system components into account. The occurrence times of hazardous events of a CTCS-3 system is quantitatively evaluated with the numerical data collected during the simulation of the system model. The evaluation results demonstrate the feasibility of the proposed approach.

Development of Mobile Robots based on Wireless Robotic Components using UML and Hierarchical Colored Petri Nets

Development of Mobile Robots based on Wireless Robotic Components using UML and Hierarchical Colored Petri Nets

The efficiency of modeling and simulation of manufacturing systems using Petri nets

The paper is a partial synthesis of the work that a team within the Faculty of Managerial and Technological Engineering has in the field of modeling and simulation of systems with Petri nets. The paper deals with three issues. The first part is Modeling and simulation of manufacturing systems with timed Petri nets. The first part presents the way in which the performances of some manufacturing systems are evaluated using timed Petri nets. The first example is a manufacturing system specific to the textile industry. The system has three production lines. In this case, the modeling with timed Petri nets allows the analysis of the operation of the flow lines and highlights the bottleneck. Another modeled manufacturing system is specific to a series production, more precisely it refers to the manufacture of gas cookers within a company from Oradea. The model with Petri nets also describes the supply sequences of the stocks of parts and subassemblies. The next modeled system is an automated manufacturing system for the packaging of detergents. The complexity of the Detergent Packing System and the high level of automation, require the use of efficient modeling and simulation methods to verify the validity of the solutions adopted. In this chapter is present the model of a robotic welding cell. The second part of the paper, the transition from timed Petri nets to hierarchical colored Petri nets, shows how Petri nets were developed for a robotic cell for metallographic analysis. The third part is dedicated to modeling with colored Petri nets timed with complex colors of the flexible manufacturing cell A007 within the Department of Industrial Engineering.

Modeling and Analysis of Network Control System Based on Hierarchical Coloured Petri Net and Markov Chain

This paper investigates a modified modeling of networked control systems (NCSs) with programmable logic controller (PLC). First, the controller-to-actuator and sensor-to-controller network-induced delays are investigated by a modeling tactics based on hierarchical coloured petri net (HCPN) in a structure-conserving way. Comparing with the recent result, the signal transmission delay is set in a random interval instead of a fixed mode; moreover, the data packet drop out and disorder are also taken into consideration. Second, delays captured form CPN tools are analyzed with a strategy based on Baum–Welch algorithm and statistics science. Besides, time delays are modeled as a Markov chain and the transition probabilities is calculated using the consequent from the previous operation. Finally, a comparison verification illustrates the equivalence property between proposed models.

Formal Verification of a Trusted Execution Environment-Based Architecture for IoT Applications

The Internet-of-Things (IoT) scenarios commonly present security and privacy concerns, either due to the processing constraints of devices or the employment of external servers to process and store data, for instance, in cloud-based IoT applications. In this sense, to protect data and decrease user distrust in external entities, security technologies are of utmost importance. Trusted execution environments (TEEs), which process data in an isolated and protected region of memory, are among these technologies. We focus on a trusted architecture solution based on the use of TEEs and the application of authentication, authorization, and encryption mechanisms to protect data in IoT applications. We specified the trusted IoT architecture (TIoTA) using hierarchical colored Petri nets, and performed simulations and model checking of key security properties related to desired and prohibited behaviors, enabling model-based testing. This article enhances the state of the art by providing project artifacts (e.g., executable and parametric models) for correctly implementing the TIoTA and by presenting evidence that the usage of the architecture can improve security and privacy.

Guaranteeing Correctness of Machine Learning Based Decision Making at Higher Educational Institutions

State-of-the-art software technologies have enabled Higher Education Institutions to record and store large amounts of student data. Analyzing this large amount of data can facilitate the decision-making process. Decisions made in higher education institutions affect policies, strategies and actions that improve education quality. It can be argued that machine learning algorithms demonstrate a remarkable ability to recognize models and predict results based on data. However, machine learning outcomes were subject to bias and erroneous labelling. Consequently, to mitigate the impact of such errors in decision making, it is necessary to put in place mechanisms to correct decision rules. This article presents an approach to learn decision rules through supervised machine learning and proves the correctness of these rules with hierarchical Coloured Petri Nets. The use of formalism in the proposed methodology ensures that the decision rules are correct and comprehensible. Empirical results show that we improved correctness with 98.68% accuracy on decision rules. This research work contributes to the improvement of the decision-making process for the academic administration of Higher Education Institutes.

Condition Monitoring System for Internal Blowout Prevention (IBOP) in Top Drive Assembly System using Discrete Event Systems and Deep Learning Approaches

Offshore oil drilling is a complex process that requires careful coordination of hardware and control systems. Fault monitoring systems play an important role in such systems for safe and profitable operations. Thus, predictive maintenance and monitoring operating conditions of drilling systems are critical to the overall production cycle. In this paper, we are addressing the topic of condition monitoring of a critical part in the process of oil drilling, the Internal Blowout Preventer (IBOP) system in the top drive assembly in offshore oil drilling. In our work, we aim to design an intelligent system for monitoring the health of IBOP system using discrete event systems (DES) based control method in combination with multivariate time series classification deep learning method. The proposed system comprises two stages: 1) produce IBOP system logical behaviour analysis using Hierarchical Colored Petri Nets (HCPN) approach; 2) develop an activity detection or a classifier module using reservoir computing framework for classification of multivariate time series for activity monitoring and fault detection for the top drive assembly.
 The combination of these methods would enable automation of monitoring and early detection of incidents during drilling operations. We present the preliminary results of a model in Petri Nets used to simulate a monitoring system for IBOP valve in top drive assembly and activity classification of activities relevant to IBOP condition monitoring. The effects of failure rate and repair time of each component on system performance are to be researched at a later stage.

Modeling with hierarchical colored Petri nets. Case study

The paper presents the results of research on the use of hierarchical models with colored Petri nets in the evaluation of automated systems for the preparation and analysis of metallographic specimens. Modeling with hierarchical colored Petri nets was used to evaluate the performance of a preparation and analysis robotic system for metallographic samples. The automated system is composed of three subsystems: the subsystem for the preparation of metallographic samples, the subsystem for the attack with reagent of metallographic samples, the subsystem for the analysis of metallographic samples. Two models were made: a model with colored Petri nets with simple colors and a model with timed colored Petri nets with complex colors. Each model was developed on two hierarchical levels. Level 1 contains the model of the entire flexible system for the preparation and analysis of metallographic samples. Level 2 consists of three sub-models: the sub-model of the system for the preparation of metallographic samples, the sub-model of the system for the reagent attack of metallographic samples, the sub-model of the system for the analysis of metallographic samples. Models with timed colored Petri nets allow the evaluation of system performance in terms of the number of samples analyzed in a time interval. The performance of the modeled system was evaluated by simulation, considering a time interval of eight hours.

Using a novel hierarchical coloured Petri net to model and optimise fleet spare inventory, cannibalisation and preventive maintenance

Spare part availability is crucial to restoring inoperative platforms to the working state. Platforms failing during operation undergo corrective maintenance to replace failed components with spares. To reduce the frequency of this unplanned, corrective maintenance, platforms are inspected periodically and degraded components preventively replaced. Maintenance delays occur when spares are unavailable but cannibalisation can reduce these delays by allowing working components to be removed from inoperative platforms and used to restore other inoperative platforms. Fleets can be deployed across multiple bases that are served by one or more depots. Failed components that cannot be repaired at a base are sent to a depot for repair, along with associated requests for spares, which are satisfied by depot inventories.The management of fleet corrective and preventive maintenance, cannibalisation, spare inventories, provision of spares to bases and depots, and response of the depot to spare requests is a complex problem for fleet maintenance managers and critical to ensuring acceptable fleet performance. This paper presents a novel hierarchical coloured Petri net (HCPN) model of a fleet spare inventory system, which accounts for these issues alongside fleet deployment and mission-oriented operation. The application of the model is demonstrated using case studies of two example fleets.

Hierarchical Coloured Petri-Net Based Multi-Agent System for Flood Monitoring, Prediction, and Rescue (FMPR)

In Punjab Pakistan, a river flood event is the most important natural disasters that every year causes high human casualties as well as heavy economic losses. A safety-critical system should be correct, reliable, complete, consistent, and unambiguous for accurate and precise flood monitoring, prediction, as well as emergency and rescue services during or after a flood event. System correctness must be ensured in every phase of the development of a safety-critical Flood Monitoring, Prediction, and Rescue (FMPR) system. Correctness is a functional property related to the behavior of the system having sub-properties of safety and liveness. These sub-properties must also be correct, complete, consistent, and unambiguous. Rigorous mathematical based software engineering methods like formal methods are suitable for the specification, design, modeling, verification, and validation of an FMPR safety-critical system. The proposed safety-critical system for FMPR is distributed as it is based on multi-agents. This system is specified, analyzed and designed by using Gaia multi-agent methodology, which is based on organizational abstractions. Gaia role model-based agent roles are specified, regular expression based liveness properties are specified, and first-order predicate calculus based safety properties are specified. Thus, safety and liveness properties are formally specified. After the detailed design phase, the system is formally modeled and verified by Hierarchical Coloured-Petri Nets (CP-Nets). As a result, a novel formal system for the specification, analysis, design, modeling, and verification of the FMPR system is proposed. This safety-critical system is distributed based on multi-agents.

Implementation of fuzzy system using hierarchical Colored Petri Nets to model flexible manufacturing cell

In Flexible manufacturing field the Fuzzy application found in to solve conflict situation, production routing, and control in the system. In present days, to produce a product according to the Delivery dates is an important issue in Flexible Manufacturing industry. In order to focus on this issue, we try to solve this problem by implementing fuzzy rules according to due dates. The fuzzy rules are divided in three sections such as Early Due Dates (EDD), Exact Due Dates (EXACT), and Over Due Dates (OVER). In this flexible cell two other parameters are part processing time and the number of tools which are described in this fuzzy rules model. The part processing time and the number of tools are described with the small, medium and large linguistic variables. The fuzzy rule based model is constructed using Hierarchical Colored Petri Nets which is suitable to define each section as a sub model. The observed results provide the overall analysis and performance of cell. The constructed manufacturing cell model also provides the detailed behaviour of each resource where resource appears as Color token values. Also, we compare the simulation results from Hierarchical Fuzzy Colored Petri Nets and Matlab fuzzy rule based design for flexible cell.

Formal model-based quantitative safety analysis using timed Coloured Petri Nets

Fault Tree Analysis (FTA) and Event Tree Analysis (ETA) are by far the most frequently used qualitative and quantitative approaches in system reliability and safety analysis such as in the railway domain. FTA and ETA explain the causalities and consequences of hazards or accidents (e.g., rail traffic accidents) in terms of linear event sequences, which are difficult to incorporate none-linear relationships such as feedback. For quantitative analysis, FTA and ETA have disadvantages in dealing with dependent failure events. The quality assurance for fault trees and events trees is mainly carried out by peer review. In addition, traditional FTA and ETA are usually applied to systems that consists of non-repairable components. For systems that comprise repairable components, Markov models are widely used, which suffer however intensively from the state space explosion.Considering all these issues, we propose a formal model-based approach for quantitative safety analysis using timed Coloured Petri Nets (CPNs). There are three main contributions in this paper: firstly, a modelling method based on the specifications of timed message sequence charts, systems theory and decision tables for system components is raised for establishing timed hierarchical CPN models of systems that are appropriate for quantitative safety analysis. Secondly, state-space-based methods by exploring standard state space reports, and applying standard as well as non-standard queries to state spaces are presented to verify the untimed CPN models. Finally, methods of evaluating the safety characteristics of mean time to hazardous event and the probability of keeping in normal and safe states on the basis of the data collected during the simulation of the timed CPN models are provided. To illustrate our approach, a case study of a railway level crossing control system is presented as a running example throughout the paper.

Hierarchical Colored Petri Nets for Modeling and Analysis of Transit Signal Priority Control Systems

In this paper, we consider the problem of developing a model for traffic signal control with transit priority using Hierarchical Colored Petri nets (HCPN). Petri nets (PN) are useful for state analysis of discrete event systems due to their powerful modeling capability and mathematical formalism. This paper focuses on their use to formalize the transit signal priority (TSP) control model. In a four-phase traffic signal control model, the transit detection and two kinds of transit priority strategies are integrated to obtain the HCPN-based TSP control models. One of the advantages to use these models is the clear presentation of traffic light behaviors in terms of conditions and events that cause the detection of a priority request by a transit vehicle. Another advantage of the resulting models is that the correctness and reliability of the proposed strategies are easily analyzed. After their full reachable states are generated, the boundness, liveness, and fairness of the proposed models are verified. Experimental results show that the proposed control model provides transit vehicles with better effectiveness at intersections. This work helps advance the state of the art in the design of signal control models related to the intersection of roadways.

FRABAC: A new Hybrid Access Control Model for the Heterogeneous Multi-domain Systems

In this paper, a new hybrid, flexible, scalable and fine-grained model, fine-grained role-attribute access control (FRABAC) is proposed. FRABAC combines the benefits of the two most popular basic models: role-based access control (RBAC) and attribute-based access control (ABAC). The new proposed model overcomes the shortcomings of both models RBAC and ABAC known as combinatorial explosion in rules and roles when the security policy becomes complicated. Besides avoiding the combinatorial explosion, the new proposed model provides a role permission agreement (APA) to handle inter organisational access decision in collaborative cloud services cases. The proposed model is applied to define the security policies in realistic case studies and results are compared to previous existing models. On the other hand, the consistency and the correctness of the built policies are analysed through a formal modelling/analysis approach. This formal approach uses hierarchical coloured Petri nets (HCPNs) to model the policy and the CPN-tools to analyse the generated models.

The Collaborative System Workflow Management of Industrial Design Based on Hierarchical Colored Petri-Net

Industrial design is a requisite and incontrovertible front-end design for Industrie 4.0 to realize personalization, agility, intelligence, and standardization, so it has very important practical significance to achieve industrial design collaborative workflow flexible management. This paper proposed a hierarchical colored Petri net (HCPN) for modeling the industrial design collaborative system workflow, which aims to provide a valid workflow model for the process management of the industrial design collaborative system. First, it is built the top-level workflow CPN model from product planning, markets research, product design, and product evaluation to prototype production, then the model is extended layer by layer to build the subnet model by the model refinement method. In the model, the activity of the workflow and the activity execution results are represented by the transitions ( $T$ ) and places ( $S$ ), respectively. The running state of the whole workflow is represented by the distribution of the token in the places. The token’ color sets expresses the real-time discrete state. By use of the function of token coloring places ( $S$ ) and the token’ color sets of HCPN, this paper extracts the common characteristics of process knowledge, including markets research results, design ideas, conceptual sketches, design schemes, human resources, and tacit creative knowledge, then uses the what, when, where, who, and how method to build knowledge information units for specific design event. Thus, realizes the industrial design process knowledge base construction and knowledge acquisition, which provides the necessary information and knowledge resources for the design reuse, flexibility management, and intelligent manufacturing of subsequent products.