基于进程代数规约生成软件体系结构模型的方法

需求规约到软件体系结构(SA)模型的转换是软件工程领域的一个研究热点,UML-RT广泛用于实时系统软件体系结构建模,然而基于自然语言规约建立的UML-RT模型往往是不精确的,存在二义性,为了解决这一问题,需要赋予UML-RT模型形式化语义.进程代数是一种用来解决并发系统通信问题的形式化方法,具有精确的语法和语义,并且便于机器自动检验与验证.TCSP是进程代数CSP的实时扩展,适合于规约实时系统带有时间约束的行为.提出一种基于进程代数规约生成SA模型的方法.首先建立了自然语言规约到SA模型的转换框架;然后使用时间通信顺序进程(TCSP)描述实时系统需求规约,通过建立TCSP到UML-RT的转换机制,从而实现进程代数规约到SA模型的转换;最后通过一个实例来验证该方法在实时软件建模过程中的有效性.实验分析表明通过该方法建立的UML-RT模型能够从整体上提高实时系统SA设计的可信性.     

使用基于进程代数的方法建立软件体系结构的安全模型

安全体系结构集成了软件体系结构与信息安全两大领域的研究,基于进程代数的语言适合描述基于并发交互构件的软件体系结构的一系列重要性质。使用基于进程代数的描述语言对结构中各组成元素和整体拓扑构形分别建模,形成安全的软件体系结构。     

基于进程代数的安全软件体系结构建模

分析了基于进程代数的软件体系结构模型的安全性,将相容性检查和互操作性检查从单个软件体系结构推广到不同风格的体系结构风格,扩展基于进程代数的软件体系结构描述语言,通过顺序进程代数项族和预定义的体系结构类型调用对软件体系结构安全建模。通过一个例子介绍了这种建模方法。     

构件组装及其形式化推导研究

基于构件的软件工程(component based software engineering,简称CBSE)能够有效地提高软件开发的质量和效率.构件组装和组装推导(compositional reasoning)是CBSE的关键技术.基于软件构件的特点,借鉴进程代数中进程构造的方法,提出6种构件组装机制,能够灵活、简便地集成软件构件,并主张在构件组装的同时进行接口组装,通过生成功能更强、抽象级别更高的复合接口,提高构件组装的抽象级别和粒度.同时,基于Wright的形式化规约软件体系结构的研究,给出了复合构件和复合接口的组装推导算法,为系统行为的形式化分析、验证和仿真奠定了基础.     

正交软件体系结构模型

当前对软件体系结构的描述通常都采用体系结构描述语言(ADb)，但ADb在对软件体系结构的动态、可进化和可扩充特征方面的描述能力明显不足。正交软件体系结构具有结构清晰、可维护性强、可移植性强、重用粒度大等优点。文章用代数理论对正交软件体系结构的属性和行为特征进行抽象，提出了正交软件体系结构的概念和框架结构，抽象出了正交软件体系结构的核心模型。提出了正交软件体系结构的抽象模型和非正交软件体系结构的正交化算法。给出了正交软件体系结构的一个应用实例。     

一种软件演化过程模型的代数语义

随着大量的软件演化过程模型被软件演化过程元模型建模产生,如何验证过程模型的正确性,是摆在人们面前的一个重要任务.针对软件演化过程元模型,引入进程代数ACP(algebra of communicating processes)对其扩展,提出软件演化过程元模型代数,使用进程项指定软件演化过程模型的代数语义,在进程代数的统一框架下,基于等式推理验证软件演化过程模型的行为,使行为验证方式从模型推导变为代数推导这种方法充分结合了Petri网和ACP的长处,可以有效地支持软件演化过程的形式验证.     

以体系结构为中心的模型转换的语义描述框架

在对类型范畴理论进行扩展的基础上,将其与进程代数相结合,为软件体系结构模型及其间的转换关系提供了一种统一的语义描述框架.模型的结构语义由类型范畴图表来指代,其行为语义则由范畴附带的进程行为迹来表示,模型间的映射关系用范畴理论中的态射和函子来形式化描述.该描述框架可用于模型转换中特性保持问题的描述、分析和判定,从而为模型驱动的软件开发提供有力的支持.     

网构软件体系结构代数模型

由于网络化软件的规模和复杂程度的不断增加,设计可伸缩的软件体系结构,开发可演化的软件系统遇到了挑战.挑战之一是很难把软件模型与原系统说明区分开来,使得软件系统的可演化性受到限制.一个有效的途径是建立可范用软件体系结构的抽象模型,指导网构软件设计,从而提高软件模型的概括能力和可伸缩能力.本文提出一种网构软件体系结构代数模型,其中一个创新思想是把网构连接子解释成网构变量的运算.结合代数学方法和软件实现技术,定义了6种网构连接运算,所有运算是对连接子的代数抽象,因此软件体系结构的抽象表达能力得到了加强.为了展示提出代数模型的建模与分析辅助作用,介绍了一个基于代数模型的网构软件设计与演化的案例研究.     

基于反射和连接件的SA动态演化研究

使用反射机制感知软件系统的结构与运行状态,提出了一种基于知识规则、直接对连接件进行操作的SA动态演化方法,消除了SA动态演化的不一致性,提高了效率.该方法使用代数表达式简化了演化日志,提高了演化可跟踪性。     

网状软件体系结构模型

文章用代数理论对网状软件体系结构的属性和行为特征进行抽象,提出了网状软件体系结构的概念,框架结构及构件的重用度概念,抽象出了网状软件体系结果的抽象模型及相关性质。给出了网状软件体系结构的相关应用。     

An efficient algorithm for aggregating PEPA models

Performance Evaluation Process Algebra (PEPA) is a formal language for performance modeling based on process algebra. It has previously been shown that, by using the process algebra apparatus, compact performance models can be derived which retain the essential behavioral characteristics of the modeled system. However, no efficient algorithm for this derivation was given. We present an efficient algorithm which recognizes and takes advantage of symmetries within the model and avoids unnecessary computation. The algorithm is illustrated by a multiprocessor example     

Formal techniques for performance analysis: blending SAN and PEPA

In this paper we consider two performance modelling techniques from the perspectives of model construction, generation of an underlying continuous time Markov process, and the potential for reduction in the Markov process. Such careful comparison of modelling techniques allows us to appreciate the strengths and weaknesses of different approaches, and facilitates cross-fertilization between them. In the present case we take a characteristic of one formalism, functional rates in Stochastic Automata Networks, and introduce it to the other formalism, Performance Evaluation Process Algebra. We investigate the benefits of this cross-fertilization, particularly from the perspectives of Markov process generation and reduction.     

进程代数及其在性能评价中的应用综述

进程代数是描述并发和通信系统的数学工具，形式化好、可操作性好，适合对复杂系统进行模型分析。本文从进程代数在计算机系统性能评价中的应用的角度对相关研究进行综述，对在此基础上开发新的形式化工具以及分析现有系统都具有指导意义。首先以CCS和PEPA为例介绍基本进程代数向随机进程代数的演进；然后阐述使用随机进程代数进行性能分析的方法，重点分析了模型简化的技术；比较了进程代数与其他性能评价方法的优缺点。     

软件体系结构性能评价研究

1 引言随着软件规模和复杂程度不断地扩大和增加,软件开发的成败已不再完全取决于数据结构和软件算法的选择,而是在很大程度上取决于软件系统体系结构(Software Architecture)的设计。软件体系结构已经成为一个新兴的计算机学科。所谓的软件体系结构是问题解决方案的逻辑框架,它包括系统中各计算单元(组件)的功能分配、各单元间的高层交     

Formal enforcement of security policies on concurrent systems

This paper introduces a formal and modular technique allowing to automatically enforce a security policy on a given concurrent system. Given a concurrent program P and a security policy ?, we automatically generate another program P^′ that satisfies ? and behaves like P, except that it stops when P tries to violate the security policy ?. We use extended version of process algebra ACP (Algebra of Communicating Process) and BPA (Basic Process Algebra) as formal languages to specify both concurrent system and security policy.     

Industrial environmental performance evaluation: A Markov-based model considering data uncertainty

Commonly, operational aspects of an industrial process are not included when evaluating the process environmental performance. These aspects are important as operational failures can intensify adverse environmental impacts or can diminish the chance of making any amelioration. This paper proposes to include these operational aspects by applying a method called Industrial Environmental Performance Evaluation. To have a reliable environmental performance measure for assisting policy-making in an organization, two types of uncertainty are considered in the proposed method. The first type is the epistemic uncertainty due to imperfect knowledge about the environmental impacts of the process. Epistemic uncertainty is considered by using the potential probability of material release during operating and non-operating periods of the process. The second type is aleatory uncertainty due to potential stochastic behaviour of the process. Aleatory uncertainty is modelled through a Markov-based model and is considered by the state probability distribution vectors. The proposed method is employed to analyze an existing formaldehyde production process as a case study. The analysis shows the relation between environmental and operational performances of the process. Process owners can use this analysis for improving the environmental and operational aspects of their process and achieve accuracy in their environmental decisions.     

Web服务编排中信息对齐交互建模方法研究

针对Web服务编排标准WS-CDL中信息对齐交互模式的异步特性,提出了一种基于进程代数的Web服务编排方法（PA4WS）,该方法新增WS-CDL工作单元描述算子,通过设置工作单元算子的卫式条件和循环条件来描述异步交互,进而完成对信息对齐交互的建模。     

基于CCS的软件规范描述及实例研究

软件规范描述方法主要是软件工程化的UML方法与形式化方法二类方法。论文主要给出了基于CCS的软件规范描述,首先根据系统需求画出进程派生树和迁移图,再根据操作语义和系统约束条件得到进程表达式,并用Java语言实现了系统原型代码。笔者的工作证明了CCS具有细节化地描述系统内部状态,便于系统软件实现的能力;在手工转换进程迁移图到进程表达式的基础上,提出了自动转换的进一步研究思路。     

Decision procedures and graph reductions for bisimulation equivalences part 1

In Process Algebra, processes are often specified in a framework of bisimulation semantics. The notion of bisimulation therefore plays an important role.

In this paper some existing and new decision methods are presented for strong bisimulation, τ-bisimulation and η-bisimulation. Each of these bisimulation equivalences corresponds to a certain abstraction mechanism.

In strong bisimulation, all events in a system are treated equally whereas τ-bisimulation takes into account the silent step τ; η-bisimulation was introduced recently for an alternative silent step η that is less abstract than τ. It is shown that the problem of η-bisimulation decision can be reduced to an abstract graph partitioning problem called the Product Relational Coarsest Partition problem. Special attention is paid to computational complexity of the decision methods.

As it turns out. finite process graphs can be reduced to unique minimal normalforms under all three bisimulation semantics mentioned.

The last section demonstrates how the decision methods can be used with a particular algebraic model to enable effective verification of specifications.     

Useful approach for evaluating expert systems

Abstract: Evaluation of expert systems is an important step in the knowledge engineering process. In recent years, emphasis has been placed on knowledge acquisition, knowledge representation, and inferencing mechanisms. However, evaluation, and to a lesser extent, validation, have been slightly overlooked. This paper addresses some of the evaluation techniques that have been used for measuring information systems effectiveness and expert systems effectiveness. Specific attention is focused on the Analytic Hierarchy Process and Expert Choice. The evaluation results of an expert system prototype, called 'Read', are discussed via the use of the Analytic Hierarchy Process and Expert Choice.