多媒体节目时序描述的组合技术

组合性是形式描述研究的基本问题,便于大型程序的设计、分析、测试和复用.为了方便用户编制大型多媒体系统的时序描述,组合模型是必须的.目前,这样的模型有基于语言的、基于图形的、基于时间区间的和面向对象的等等.但是,这些模型描述层次过低,很难支持两个多媒体节目之间的时序描述.通过引入单位流的概念和扩展两种时序关系,研究一种多媒体节目时序描述的结构化技术,使复杂的多媒体节目易于理解,以方便用户运用组合方法把一些可以复用于不同多媒体节目的节目模块进行组合设计.     

时态逻辑与程序验证

近年来,时态逻辑大量应用于程序验证,采取的途径随使用的时态逻辑的形式和方法的不同而异。本文用自动机理论研究几种时态逻辑(LTL,BTL,POTL)的模型和模型生成子,并讨论用时态逻辑进行程序验证的的重要途径。     

SPVT:一个有效的安全协议验证工具

描述了基于Objective Caml开发的一个安全协议验证工具SPVT(security protocol verifying tool).在SPVT中,以扩展附加项的类(演算作为安全协议描述语言,以扩展附加项的Horn逻辑规则描述协议攻击者的Dolev-Yao模型,通过一组抽象规则将安全协议的类(演算模型转换为逻辑程序模型,基于安全协议逻辑程序的不动点计算验证安全性质,从安全协议逻辑程序的不动点计算和安全性质的验证过程中构造不满足安全性质的安全协议反例.以简化的Needham-Schroeder公钥认证协议为例,描述了使用SPVT自动验证安全协议的过程,表明了SPVT用于安全协议验证的有效性.     

Using Program Transformations to Provide Safety Properties for Real-Time Systems

The process of showing that a program satisfies some particular properties with respect to its specification is called program verification. Axiomatic semantics is a verification method that makes assertions describing properties about the states of a program. There exists a transformation from the assertions of a program's verification proof to executable assertions. The latter may be embedded in the program to make it fault tolerant. An axiomatic proof system for concurrent programs is applied to generate executable assertions in a real time distributed environment. A train set example is used as modelproblem.     

基于时序逻辑证明编译优化程序变换的保义性

基于时序逻辑CTL(computation tree logic)的一种扩展CTL-FV对优化编译中的语句交换和变量替换这两种常见变换的保义性条件给出了形式刻画,采用含条件重写规则定义了保义语句交换T_exch和保义变量替换T_sub,并基于一种归纳证明框架对它们的保义性进行了证明.此外,基于变换Texch对程序基本块内保依赖语句重排的保义性也给出了一种构造性的证明.     

Validation of HOL Proofs by Proof Checking

Formal proofs generated by mechanised theorem proving systems may consist of a large number of inferences. As these theorem proving systems are usually very complex, it is extremely difficult if not impossible to formally verify them. This calls for an independent means of ensuring the consistency of mechanically generated proofs. This paper describes a method of recording HOL proofs in terms of a sequence of applications of inference rules. The recorded proofs can then be checked by an independent proof checker. Also described in this paper is an implementation of a proof checker which is able to check a practical proof consisting of thousands of inference steps.     

基于Hoare逻辑的密码软件形式化验证系统

在Hoare逻辑理论和ACSL语法规范的基础上,设计一种针对密码软件的形式化验证系统,由程序规范、验证推理规则、可靠性策略、验证推理等模块组成。以OpenSSL中RC4算法的软件实现为例,对其功能正确性、保险性和信息流安全性进行验证,结果表明,该系统具有较高的自动化水平,可在一定程度上降低形式化验证方法的复杂度。     

Collecting Statistics Over Runtime Executions

We present an extension to linear-time temporal logic (LTL) that combines the temporal specification with the collection of statistical data. By collecting statistics over runtime executions of a program we can answer complex queries, such as “what is the average number of packet transmissions' in a communication protocol, or “how often does a particular process enter the critical section while another process remains waiting' in a mutual exclusion algorithm. To decouple the evaluation strategy of the queries from the definition of the temporal operators, we introduce algebraic alternating automata as an automata-based intermediate representation. Algebraic alternating automata are an extension of alternating automata that produce a value instead of acceptance or rejection for each trace. Based on the translation of the formulas from the query language to algebraic alternating automata, we obtain a simple and efficient query evaluation algorithm. The approach is illustrated with examples and experimental results.     

一种自动的形式化验证技术-模型检测

模型检测是针对有限状态系统行为的逻辑性质的一种自动验证技术,已有许多工业应用.其主要缺陷是空间爆炸问题.本文通过一简单实例介绍其基本思想、检测步骤和相关理论,给出一些处理状态空间爆炸问题的优化技术,并与其它验证方法进行了比较,最后简单介绍了软件模型检测的新进展.     

An approach to systems verification

The term systems verification refers to the specification and verification of the components of a computing system, including compilers, assemblers, operating systems and hardware. We outline our approach to systems verification, and summarize the application of this approach to several systems components. These components consist of a code generator for a simple high-level language, an assembler and linking loader, a simple operating system kernel, and a microprocessor design.     

用高阶逻辑表达时态逻辑及其应用

硬件设计的形式化验证技术开辟了对复杂的超大规模集成电路设计进行验证的新途径。高阶逻辑和时态逻辑在形式化验证技术中均得到成功的应用。本文介绍用高阶逻辑表达线性时态逻辑和区间时态逻辑的方法，并以几个简单实例说明它在硬件设计验证中的应用。这种方法的优点是既利用高阶逻辑系统ＨＯＬ的机械化定理证明手段，又发挥了时态逻辑的表达硬件的动态性质的能力。     

Hybridity in Embedded Computing Systems

An embedded system is a system that computer is used as a component in a larger device.In this paper,we study hybridity in embedded systems and present an interval based temporal logic to express and reason about hybrid properties of such kind of systems.     

一个支持位运算形式化推理的抽象机

程序推理使用的抽象机器与物理机器的差距降低了推理的精确度,为了缩小这个差距,本文提出了一个带位级别抽象的新抽象机,在这个机器里,二进制整数以纯语法的方式被表示成位矢量而不是非负整数.使用这个抽象机器,可以在其上进行许多带位操作指令的程序,特别是系统级代码的Hoare逻辑风格推理.本文中,二进制整数及其上的算术逻辑运算使用Coq的归纳结构演算来形式化,并且一些常见的重要性质也都使用Coq证明助理进行了严格的形式化证明.     

New and used temporal models: An issue of time

TheSpecial Issue on Applications of Temporal Models raises many issues of time: What are the important properties of time? How can time be best represented? How can one reason about time-dependent properties? What are the important directions of temporal research? This introductory piece very briefly surveys the current wide variety of temporal models, temporal reasoning methods, and applications to time-varying phenomena. Promising areas of investigation such as the verification of concurrent systems, knowledge-base representation methods, and dealing with theFrame Problem pass in fleeting review. Brief introductions to each of the works in the volume close the section.     

一种基于定理证明的Web服务合成方法研究

随着Internet中Web服务的不断增长,如何通过对现存的服务进行合成,以满足用户的个性化需求,成为目前的研究热点。通过引入线性逻辑工具,提出了一种新的Web服务合成解决方案,通过定理证明形成对应的自动服务合成流程。示例证明了该方法的有效性。     

硬件构件的形式化描述及其组装机制

针对构件化的路由交换平台设计,提出硬件基础构件的抽象模型及其内部处理流程的形式化描述,提取出顺序、并行、分支以及聚合4种原子组装机制,用于构建更高层次的复合构件,并推导出复合构件抽象模型及其处理流程的形式化描述,从而有利于抽象出更大粒度的构件用以组装复杂的硬件平台。     

实时系统的形式化验证

实时系统的设计对系统设计人员而言是一个巨大挑战。在缺乏严格的验证环境时 ,要避免设计错误是很困难的。本文将一种带时戳的时序逻辑及用于描述具体实时系统的时间变迁系统编码到 HOL定理证明器中 ,并实现了一个基本的规则策略库 ,从而实现了一个简单的交互式辅助验证环境L RP。实例 Fisher算法的互斥性在 IRP中得到了验证。