Petri net as a modeling tool

Over the last decade, Petri nets have emerged as a most suitable, powerful and widely acceptable modeling tool for representing and studying the asynchronous concurrent hardware (or software) systems/processes. Petri nets can be viewed as formal automata or as an automation which can generate the formal languages or a model to analyse and synthesize various kinds of systems. The structure of Petri nets, their markings, extensions and subclasses are briefly discussed. Several examples of Petri net models of computer hardware and software are presented. Various applications of reachability concepts are also given.     

System Prototype and Verification Using Metamodel-Based Transformations

Mapping domain-specific languages' core concepts into the concurrent object-oriented Petri nets formal specification language provides users with the semantics necessary for developing prototypes for these DSLs. Different knowledge domains demand different types of support from software languages. Domain engineers often use domain-specific languages to overcome this problem. DSLs are difficult to design, implement, and maintain and are often less efficient than hand-coded software. To address some of these problems, we propose transforming a DSL into the concurrent object-oriented Petri nets formalism. The DSL metamodel serves as the transformation's starting point. The transformation represents the semantic mapping between the DSL and CO-OPN. We aim both to provide a formally defined semantics for the DSL and, because we integrate CO-OPN in a framework, to provide the functionalities that allow model verification and fast prototype generation for the DSL     

Mobile medical visual information retrieval

In this paper, we propose mobile access to peer-reviewed medical information based on textual search and content-based visual image retrieval. Web-based interfaces designed for limited screen space were developed to query via web services a medical information retrieval engine optimizing the amount of data to be transferred in wireless form. Visual and textual retrieval engines with state-of-the-art performance were integrated. Results obtained show a good usability of the software. Future use in clinical environments has the potential of increasing quality of patient care through bedside access to the medical literature in context.     

Performance study of a wireless mobile ad hoc network with orientation‐dependent internode communication scheme

A Petri‐net‐based simulation model of a wireless mobile ad hoc network is developed and studied. The model covers all the fundamental aspects of behaviour of such a network and uses a novel scheme of orientation‐dependent (or sector‐dependent) internode communication, with random states of links. The proposed scheme enables representation of reliability aspects of wireless communication, such as fading effects, interferences, presence of obstacles and weather conditions in a general and rather easy way. The simulation model was implemented in terms of a class of extended Petri nets to explicitly represent parallelism of events and processes in the WLAN as a distributed system. In the simulation, the behaviour of four fundamental performance metrics — packet delivery ratio, average number of hops, relative network traffic and end‐to‐end delay — were investigated with varying distance of transmission and different combinations of model parameters. Copyright © 2012 John Wiley & Sons, Ltd.     

Model-driven software synthesis for hard real-time applications with energy constraints

Model-driven methods have been quite effective for reducing the intricacies of embedded software development, since they provide effective means for property verification as well as automatic code generation. Nevertheless, regarding energy-constrained hard real-time systems, few model-driven methods are available and, usually, most methods (model-driven or not) consider simplified system specifications, such as absence of intertask relations. This paper presents a model-driven method for software synthesis of hard real-time embedded applications with energy constraints. A formal model based on time Petri nets is adopted in order to provide a basis for pre-runtime schedule generation and property analysis/verification.     

Modeling, analysis, simulation, scheduling, and control ofsemiconductor manufacturing systems: A Petri net approach

This paper presents a Petri net approach to modeling, analysis, simulation, scheduling, and control of semiconductor manufacturing systems. These systems can be characterized as discrete event systems that exhibit sequential, concurrent, and conflicting relations among the events and operations. Their evolution is dynamic over time. The system complexity is tremendous owing to the complex semiconductor manufacturing processes and test procedures. A formal approach such as Petri nets enables one to describe such complex discrete event systems precisely and thus allows one to perform both qualitative and quantitative analysis, scheduling and discrete-event control of them. This paper also serves as a tutorial paper. It briefly reviews applications of Petri nets in semiconductor manufacturing automation. It then introduces definitions and concepts of Petri nets. It proceeds with a discussion of basic Petri net modules in system modeling, a modeling method and a practical system's modeling example. Next, the paper presents their properties and their implications in manufacturing systems, as well as their analysis methods. Timed Petri nets are introduced for system simulation, performance evaluation, and scheduling purposes. An application-oriented case study is presented. Finally, the paper concludes with the active research areas in applying Petri nets to design of semiconductor manufacturing systems     

Availability modeling of energy management systems

Energy management system (EMS) computer architectures have changed significantly over the recent past increasing the difficulty and the need for a priori assessment of system performance and dependability. The old practice based on measurements is no longer acceptable because of the flexibility accrued with the deployment of the new distributed computer-based systems. The number of “what if” questions increased since EMS systems are now implemented using multiple workstations that can be interconnected in various different ways.In this paper we show how alternative configurations can be modeled and analyzed, before proposing and purchasing any equipment, with the assistance of Markov reward models. We review the concept of Markov reward models and show how they can be applied in the availability analysis of SCADA/EMS computer systems. The paper also presents a software tool that facilitates automatic generation and solution of large Markov reward models. The input language of this modeling tool uses a variation of stochastic Petri nets called stochastic reward nets, which are also reviewed. We believe this is the first time a detailed quantitative model of a SCADA/EMS computer system is proposed and solved in the general literature.     

A new generalized stochastic Petri net modeling for energy-harvesting-wireless sensor network assessment

This paper proposes an energy-harvesting-aware model that aims to assess the performances of wireless sensor networks. Our model uses generalized stochastic Petri nets to define a sensor–neighbors relationship abstraction. The novelty of the proposed formulation is taking into account several real-life considerations such as battery-over breakdowns, unavailability of neighbors, retrial attempts, and sleeping mechanism in a single model. We use TimeNet tool to simulate the network behavior in order to evaluate its performance throughout different formulas after it had reached its steady state. Finally, we present a case study featuring the different solar energy recovery capabilities of the vast Algerian territory. The aim is to show with the presented model how to determine the kind of resources to be acquired in order to cope with the sensor deployment project requirements. The proposed model allows us to ensure that the battery energy level of sensors deployed in Algiers province for example is almost equal to 80% for 100 messages per day and (1 min/2 min) for (awakening time/sleeping time) ratio.     

用于检测数据库一致性的Petri网模型

本文通过建立事务调度的Ｐｅｔｒｉ网模型，给出了并发控制系统判断数据库一致性的形式化方法，得到了判定可串行化调度的充要条件。本方法简便、实用，大大改进了以往的方法，为实现数据库一致性的自动判定提供了前提。最后从方法学角度提出了应用Ｐｅｔｒｉ网的新方法。     

Synchronization and storage models for multimedia objects

A technique is presented for the formal specification and modeling of multimedia composition with respect to intermedia timing. The proposed model is based on the logic of temporal intervals and timed Petri nets. A strategy is evinced for constructing a database schema to facilitate data storage and retrieval of media elements based on the temporal relationship established by the proposed modeling tool. An algorithm which allows the retrieval of media elements from the constructed database in a manner which preserves the temporal requirements of the initial specification is presented. Using the proposed model, the synchronization requirements of complex structures of temporally related objects can be easily specified     

Performance Analysis of SyncML Server System Using Stochastic Petri Nets

Synchronization Markup Language (SyncML) is a specification of a common data synchronization framework for synchronizing data on networked devices. SyncML is designed for use between mobile devices that are intermittently connected to a network and network services that are continuously available on the network. We have designed and developed a data synchronization system based on the SyncML protocol and evaluated the throughput of the system using the stochastic Petri nets package (SPNP) and analyzed the relationship between the arrival rate and the system resources. Using this model, we evaluate various performance measures in different situations, and we estimate the relationship between the arrival rate and the system resources. From the results, we can estimate the optimal amount of resources due to the arrival rate before deploying the developed system.     

Integrated scheduling of flexible manufacturing systems employingautomated guided vehicles

Centralized and distributed automated guided vehicle system (AGVS) models for materials handling, and the model for part processing are integrated into a single coherent model. This formulation can be used to collectively schedule and control the entire flexible manufacturing system (FMS) as opposed to the traditional separate scheduling of part processing and material handling. The two AGVS models are based on Petri nets and can be directly used in the scheduling method that uses Petri nets for formulation and heuristic search for solution. This method employs a global search to seek the optimal operation of an entire FMS. Scheduling examples are presented and the method compares favorably with the results simulated using heuristic dispatch rules     

基于PETRI网模型的LEO/MEO/GEO三层卫星网络的性能分析

基于Petri网模型方法和仿真方法,对一种低轨/中轨/同步地球轨(LEO/MEO/GEO)三层卫星网络进行了性能分析.首先建立了卫星网络的广义随机Petri网(GSPN)模型,采用SPNP6.0软件进行了网络性能分析.然后,将分析结果与采用OPNET软件对该三层卫星网络模拟的结果进行了比较,验证了模型的正确性,并得出了诸如在高网络负载的情况下三层网络结构的性能优于单层等新的结论.     

基于FPGA的有色Petri网仿真系统设计

为了实现大规模有色Petri网模型的性能测试,设计了基于FPGA的高速仿真系统。该系统实现了库所、变迁模块到硬件结构的映射,采用C语言实现了有色Petri网的硬件自动生成工具。通过分析有色Petri网的特征,该工具生成对应的Verilog代码和基于Quartus的自动脚本。以通信中"包传输"的模型为例,在FPGA中对生成的代码进行测试,验证了设计的正确性。     

New architecture for enforcing multimedia synchronization in videoconferencing applications

This paper presents a formally defined architecture allowing the design and the corresponding implementation of a set of modules that fulfill the quality of service requirements of PNSVS (Petri Net Synchronized Videoconference System), an application designed to run on top of an asynchronous environment. It describes the mechanisms and architecture allowing the system to enforce the temporal synchronization between the audio and video streams, the presentation quality, and the end to end delay. This synchronization method relies on a formal model extending time Petri nets: the Time Stream Petri Net (TSPN) model, that will be used to completely specify the time constraints of the application streams. From this, the communication architecture is improved by introducing a new partial order transport service that maximizes the PNSVS quality of service. The partial order transport principle is presented together with the pre-synchronization sub-layer, which makes the partial order transport service match the applicative synchronization requirements. Moreover, it will be shown that each layer of this synchronization architecture can be formally modeled by a well defined set of TSPN models.     

Structuring and composability issues in Petri nets modeling

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