Software Design Representation Using Abstract Process Networks

An approach to software design representation which is consistent with the concept of engineering blueprints is presented. The main criteria for software engineering blueprints are defined and a network scheme of graphical representation is considered through an overview of Petri net techniques. The concept of an abstract process (AP) is introduced as the basic element of system representation. An abstract process network schema of software design representation is developed and supported by an algebraic system of notation. Methods of AP-net construction are presented and illustrated by examples. The advantages of using the proposed approach in different phases of software engineering are pointed out and the main directions for further research have been identified.     

Mobility and Extensibility in the StratOSphere Framework

We describe the design and implementation of our StratOSphere project, a framework which unifies distributed objects and mobile code applications. We begin by first examining different mobile code paradigms that distribute processing of code and data resource components across a network. After analyzing these paradigms, and presenting a lattice of functionality, we then develop a layered architecture for StratOSphere, incorporating higher levels of mobility and interoperability at each successive layer. In our design, we provide an object model that permits objects to migrate to different sites, select among different method implementations, and provide new methods and behavior. We describe how we build new semantics in each software layer, and present sample objects developed for the Alexandria Digital Library Project at UC Santa Barbara, which as been building an information retrieval system for geographically-referenced information and datasets. We have designed using StratOSphere a repository that stores its holdings. The library's map, image and geographical data are viewed as a collection of objects with extensible operations. StratOSphere.     

Compositional semantics of a real-time prototyping language

The formal semantics of a prototyping language for hard real-time systems, PSDL, is given. PSDL provides a data flow notation augmented by application-orientation timing and control constraints to describe a system as a hierarchy of networks of processing units communicating via data streams. The semantics of PSDL are defined in terms of algebraic high-level Petri nets. This formalism combines algebraic specifications of abstract data types with process and concurrency concepts of Petri nets. Its data abstraction facilities are used to define the meaning of PSDL data types, while high-level Petri nets serve to model the casual and timing behavior of a system. The net model exposes potential concurrency of computation and makes all synchronization needs implied by timing and control constraints explicit and precise. Time is treated as state of clocks, and clocks are modeled as ordinary system components. The net semantics provides the basis for applying analysis techniques and semantic tools available for high-level Petri nets     

A parallel distributed control architecture for multiple robot systems using a network of microcomputers

This paper presents the design and implementation of a parallel distributed control architecture for industrial multiple robot systems. The design methodology is based on a concept of discrete states and actions, and a robotic task is represented as a sequence of primitive actions. For cooperative or exclusive tasks at the synchronous level of multiple robot systems, Petri net representation is applied, and discrete event-driven control is implemented as a data flow network of concurrent processes communicating with each other. Implementation of multiprocessing control on a microcomputer and a network of microcomputers is discussed.     

Net-VE系统中动态共享状态管理方法的研究

本文介绍了net VE系统中动态共享状态管理的三种方法及其优缺点,分析了如何使用分布式数据库来管理net VE中的共享状态,讨论了与分布式数据库的接口设计、接口要完成的主要功能、数据库中要存储的对象类型、共享状态的更新策略等。     

A knowledge intensive multi-agent framework for cooperative/collaborative design modeling and decision support of assemblies

Multi-agent modeling has emerged as a promising discipline for dealing with decision making process in distributed information system applications. One of such applications is the modeling of distributed design or manufacturing processes which can link up various designs or manufacturing processes to form a virtual consortium on a global basis. This paper proposes a novel knowledge intensive multi-agent cooperative/collaborative framework for concurrent intelligent design and assembly planning, which integrates product design, design for assembly, assembly planning, assembly system design, and assembly simulation subjected to econo-technical evaluations. An AI protocol based method is proposed to facilitate the integration of intelligent agents for assembly design, planning, evaluation and simulation process. A unified class of knowledge intensive Petri nets is defined using the O-O knowledge-based Petri net approach and used as an AI protocol for handling both the integration and the negotiation problems among multi-agents. The detailed cooperative/collaborative mechanism and algorithms are given based on the knowledge objects cooperation formalisms. As such, the assembly-oriented design system can easily be implemented under the multi-agent-based knowledge-intensive Petri net framework with concurrent integration of multiple cooperative knowledge sources and software. Thus, product design and assembly planning can be carried out simultaneously and intelligently in an entirely computer-aided concurrent design and assembly planning system.     

基于Petri Net软件体系结构模型的描述

软件体系结构是软件工程中一个新兴的研究热点,但是没有一个比较通用的描述规范。因此体系结构的完整性、一致性和正确性等都无法保证。该文提出的一个PetriNet的扩展理论,给出了抽象库所和抽象变迁的概念,为构件的信息隐藏、控制流的抽象提供了可能;同时对重用有特别意义的继承机制在PN中的表示进行了比较详细介绍,吸取了PN强大而完整的描述能力,严谨的验证体系。为软件体系结构描述的正确性提供了一个比较简单,但是完整的基于Net的描述方法。     

Petri网共享T型子网合成结构性质分析及其应用

为了解决系统设计中的子系统共享问题，提出了经由Petri网共享T-型子网构成共享T-型子网合成网的解决方案；研究了共享T-型子网合成网的结构性质，提出了共享T-型子网合成网保持结构有界性、守恒性、可重复性、相容性、P-不变量、T-不变量、公平性和结构活性的充分条件或充要条件；特别在证明结构活性保持性的过程中，体现了Petri网层次化的描述方法。本文的结果可为Petri网系统合成性质的考察提供有效途径，为复杂大系统的分析提供重要手段，并特别适合于一类系统的设计和分析，具有一定的实用价值。     

Modeling and synthesis of supervisory control based on Petri nets for distributed objects. I. Interaction mechanism and the basic method

We describe a methodology of discrete event modeling for a class of distributed objects and their required behavior (specifications) for the design of real time automation systems. In our methodology, we use the structured discrete event system (SDES2) model: on the first stage, it is used to analyze the functionality and coherence of the object and its specification; on the second, we propose for SDES2 a basic synthesis method that works for the models of object and supervisor based on Petri nets (both modeling and controlling). At the same time, we propose to synthesize the supervisor as a Petri net embedded in SDES2 with a feedback circuit in order to restrict the object’s operation according to specification requirements. We propose an interaction mechanism for the modeling and controlling Petri nets with the object and the external environment. In essence, the interaction mechanism is an object control scheme based on the constructed net. This mechanism analyzes the current state of the object and computes the controls that should be passed on to the object’s actuators. Computations are done with a cyclic procedure looping over the matrix representation of the net.     

基于数据集约束的并行数据流建模与描述研究

为了简化带有数据集约束的抽象网格工作流语言(AGWL)的工作流建立过程,提出了一种基于扩展面向对象Petri网(DOPN)建模并行数据流的方法.研究了AGWL并行数据流的特点,在此基础上对面向对象Petri网进行扩展,设计了基于扩展面向对象Petri网描述的并行数据流模型,之后定义一套从DOPN到AGWL的映射规则.最后通过一个应用实例对一个带有数据集约束的数据流建立DOPN描述,并生成AGWL数据流代码.该方法简化了AGWL工作流建立过程,并保留了流程验证和仿真的扩展性.     

Synthesis of Controllers of Processes Modeled as Colored Petri Nets

This paper presents an adaptation of a supervisory control theory and a supervisor synthesis problem to a class of colored Petri nets. More specifically, the forbidden state control problem with full observation, in which a discrete-event system is modeled as a colored Petri net with a symmetry specification, is investigated. This problem is decidable if the colored Petri net has finite color sets and bounded places. A new algorithm for deriving a controller is presented in detail with a proof of correctness. Unlike conventional algorithms that explore the entire reachable set of states, our algorithm avoids an exhaustive search of the state space by exploiting a symmetry specification. It performs particularly well when applied to large but structured processes with similar components. Furthermore, this approach leads to a representation of controllers which are smaller than those obtained with automaton-based approaches.     

基于Petri网的网格系统形式定义

Petri网有严格的数学定义,具有描述分布式通信计算系统的能力.通过分析网格系统的特点,高度抽象网格系统概念,基于Petri网原理,构造网格系统的库所和变迁,用有色Petri网系统给出网格系统的形式化定叉,并对相关概念进行了讨论.     

Software modeling and analysis using a hierarchical object-oriented Petri net

Petri net is used widely to analyze and model various systems formally. Recently, many Petri nets mania devote their efforts to enhancing and extending the expressive power of Petri nets. One such effort is to extend Petri nets with object-oriented concepts. An object-oriented paradigm provides excellent concepts to model real-world problems. Object-oriented concepts allow us to build software systems easily, intuitively, and naturally. Although several high-level Petri nets with the concept of objects are suggested, these nets do not fully support the object-oriented concepts. In this paper, we propose a hierarchical object-oriented Petri net (HOONet). The formal syntax and semantics of HOONet are explained in detail. HOONet supports a wide range of object-oriented features including abstract, encapsulated and modularized objects, object interaction by message passing, inheritance, and ploymorphism. HOONet also supports a variety of modeling and analysis mechanisms such as incremental modeling of evolving systems, unfolding the HOONet to lower level Petri net, and incremental reachability analysis for HOONet models. We demonstrate the usefulness of HOONet by applying it to modeling and analysis with an example.     

基于Petri网的分布式系统并发进程的死锁检测

分布式系统中的并发进程具有明显的并发、异步及分布性,而Petri网是模拟与分析并发、异步、分布式系统的有效工具.为此通过引入Petri网,给出了分布式系统局部并发进程等待的Petri网模型及死锁检测方法,提出了全链路合成的概念,利用全链路合成技术组装了全局并发进程等待的Petri网模型,给出了判断整个系统是否出现死锁的充分必要条件.     

Integrating Bulk-Data Transfer into the Aurora Distributed Shared Data System

The Aurora distributed shared data system implements a shared-data abstraction on distributed-memory platforms, such as clusters, using abstract data types. Aurora programs are written in C++ and instantiate shared-data objects whose data-sharing behaviour can be optimized using a novel technique called scoped behaviour. Each object and each phase of the computation (i.e., use-context) can be independently optimized with per-object and per-context flexibility. Within the scoped behaviour framework, optimizations such as bulk-data transfer can be implemented and made available to the application programmer. Scoped behaviour carries semantic information regarding the specific data-sharing pattern through various layers of software. We describe how the optimizations are integrated from the uppermost application-programmer layers down to the lowest UDP-based layers of the Aurora system. A bulk-data transfer network protocol bypasses some bottlenecks associated with TCP/IP and achieves higher performance on an ATM network than either TreadMarks (distributed shared memory) or MPICH (message passing) for matrix multiplication and parallel sorting.     

基于Petri网的FMS物流系统建模与仿真

在建立FMS物流系统Petri网模型的基础上,采用“映射”思想,将Petri网模型转化为物流系统的仿真程序,提出了库所映射为程序数据、变迁映射为程序函数、系统子网映射为FMS系统基本类的映射方法,通过实例仿真验证了软件程序与模型的一致性。     

Markov nets: probabilistic models for distributed and concurrent systems

For distributed systems, i.e., large complex networked systems, there is a drastic difference between a local view and knowledge of the system, and its global view. Distributed systems have local state and time, but do not possess global state and time in the usual sense. In this paper, motivated by the monitoring of distributed systems and in particular of telecommunications networks, we develop a generalization of Markov chains and hidden Markov models for distributed and concurrent systems. By a concurrent system, we mean a system in which components may evolve independently, with sparse synchronizations. We follow a so-called true concurrency approach, in which neither global state nor global time are available. Instead, we use only local states in combination with a partial order model of time. Our basic mathematical tool is that of Petri net unfoldings.     

Network-centric control based on Petri nets in the structured discrete-event system

Using the concepts of network-centric control, we develop a design methodology for a controlling Petri net in real-time automation systems. The methodology involves the structured discrete-event system (SDES) model to analyze the functionality and coherence of the object. We define structure of the model, as well as propose a technique for analyzing and modeling the object via the process Petri net. Finally, we suggest an analysis technique for the process Petri net and develop a design method for a supervisor, i.e., a controlling Petri net which implements the SDES specification (in coherence with the process net).