Analysing Internet Software Retrieval Systems: Modeling and Performance Comparison

Nowadays, there exist web sites that allow users to retrieve and install software in an easy way. The performance of these sites may be poor if they are used in wireless networks; the reason is the inadequate use of the net resources that they need. If these kinds of systems are designed using mobile agent technology the previous problem might be avoided. In this paper, we present a comparison between the performance of a software retrieval system especially designed to be used in a wireless network and the performance of a software retrieval system similar to the well-known Tucows.com web site. In order to compare performance, we make use of a software performance process enriched with formal techniques. The process has as important features that it uses UML as a design notation and it uses stochastic Petri nets as formal model. Petri nets provide a formal semantics for the system and a performance model.     

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     

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.     

CORBA规范的形式化描述及分析

CORBA为构建大规模分布式应用程序提供了一套公共对象服务规范,其规范主要以IDL语言编写,只提供对象的静态行为描述．提出并应用扩展有色Petri网对CORBA对象进行形式化模拟和分析,结果表明扩展有色Pctri网模型不仅能够清楚描述对象的静态行为,同时也能较好地模拟对象分布性和动态行为．     

一种基于逻辑Petri网的过程挖掘方法

逻辑Petri网是抑制弧Petri网和高级Petri网的抽象和扩展,可在过程挖掘中简洁准确的表示活动之间复杂的业务逻辑关系.本文在传统Petri网挖掘方法的基础上,为了进一步提高复杂系统挖掘模型的简洁度和拟合度,尤其是对并行活动间存在复杂与或关系的系统,提出了一种基于逻辑Petri网的过程挖掘方法,并给出了逻辑Petri网中逻辑变迁的挖掘算法.它可以充分挖掘活动之间的业务逻辑,并且业务逻辑可用逻辑表达式表示.通过与相应Petri网模型的实例比较分析,例证了本文方法的正确性和有效性,且逻辑Petri网模型更加适合日志行为.     

Differential Petri net models for industrial automation and supervisory control

Supervisory control systems play a central role in modern industrial automation. However, control theory has recently made significant advances in modeling mixed continuous/discrete event systems ("hybrid control systems"), whose typical instantiations include the industrial supervisory controller. This article shows how differential Petri nets, a model for hybrid control systems, can be used to represent industrial supervisory systems in a unified way. Typical industrial automation tests can be modeled, whereas the effect of communication protocols and software can be straightforwardly included using conventional Petri nets. Therefore, a global model for the operation of an industrial control system can be formed and its behavior analyzed.     

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     

Modeling and analysis of message passing in distributedmanufacturing systems

This paper addresses the information flow between devices and programs in computer integrated manufacturing systems. Specifically, it presents modeling techniques and methods for detecting the existence of message paths among hardware and software components and the upper bound on time delays along that message path. The modeling technique can be used to analyze interoperability between hardware and software components in the system in initial design and specification. The modeling technique has three components: an object model to describe the message passing protocols between communicating components; a color timed Petri net to describe the dynamic behavior and state dependency within each individual component; and an object synthesis method that integrates the Petri nets of individual objects and message protocols between objects to describe the dynamics of the entire system. The graphical modeling can enhance communication among different groups involved in system design and the analytical method can provide component specifications. The use of the modeling technique and method in early system design can result in time and cost savings in system integration due to better communication, better component selection and early problem identification     

Comparing ladder logic diagrams and Petri nets for sequencecontroller design through a discrete manufacturing system

Design methods for sequence controllers play a very important role in advancing industrial automation. The increasing complexity and varying needs of modern discrete manufacturing systems have challenged the traditional design methods such as the use of ladder logic diagrams (LLDs) for programmable logic controllers. The methodologies based on research results in computer science have recently received growing attention by academic researchers and industrial engineers in order to design flexible, reusable, and maintainable control software. Particularly, Petri nets are emerging as a very important tool to provide an integrated solution for modeling, analysis, simulation, and control of industrial automated systems. This paper identifies certain criteria to compare LLDs and Petri nets in designing sequence controllers and responding to the changing control requirements. The comparison is performed through a practical system after introducing “real-time Petri nets” for discrete-event control purposes. The results reported in this paper will help: (a) further establish Petri net based techniques for discrete-event control of industrial automated systems; and (b) effectively convince industrial practitioners and researchers that it is worthy and timely to consider and promote the applications of Petri nets to their particular discrete-event control problems     

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。     

Performability of integrated software-hardware components ofreal-time parallel and distributed systems

A method for analyzing performability of the integrated software-hardware components of parallel and distributed systems is presented. The technique uses generalized stochastic Petri nets at the system level (analysis of integrated software-hardware systems). The intractable problem of evaluating a parallel software environment consisting of interacting fault-tolerant parallel tasks is addressed. This is accomplished using a decomposition technique at the task-graph level, where the task graph is decomposed into segments. Recovery blocks are effectively modeled in the interacting parallel modules as well as their supporting hardware. This method greatly facilitates the analysis of performability at the system level. However, the integrated performability model increases the size of the Markov generator matrix. This issue is addressed, and a performability decomposition technique at the task-graph level presented is illustrated by a simple example of a radar command center     

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.     

Modeling and simulation of an electronic component manufacturingsystem using hybrid Petri nets

Modelling and analysis for the design and operation of manufacturing systems is a vital need. For semiconductor manufacturing systems, which are large scale systems, discrete Petri nets do not constitute an adequate tool for modeling and analysis. In fact, use of discrete Petri nets is confronted with tile state explosion and the high cost of simulation. In this paper, hybrid Petri nets are presented as powerful tools for modeling and simulation of semiconductor manufacturing systems. This model has been used for modeling and simulation of a real life electronic components manufacturing system. It provides an accurate and first simulation of this system     

A modeling framework to evaluate performability parameters ingracefully degrading systems

A systematic approach to modeling and assessing gracefully degrading systems, exploiting the formalism offered by Petri nets, is provided. The procedure followed is based on the definition of some fundamental modules, the composition of which allows a complete model of the system to be obtained. The model can then be solved by computer simulation or analytically by means of a class of Petri nets to obtain interesting performability parameters either at steady state or when the system is time-varying. A number of real cases are examined and the results obtained are described     

Modelling and scheduling hard real-time biomedical systems with timing and energy constraints

Several biomedical systems are considered time-critical in the sense that, if timing constraints are not met, catastrophic issues may occur, such as loss of human lives. Besides, some of these systems have to rely on constrained energy sources (e.g. a battery) for operating in remote locations. In this case, energy saving becomes of utmost importance in order to prolong equipment operation. Presented is a method for hard real-time systems scheduling considering dynamic voltage scaling, precedence and exclusion relations. The proposed approach adopts a formal model based on time Petri nets in order to find a feasible schedule using a pre-runtime approach that satisfies timing and energy constraints.