嵌入式实时系统的快速开发框架研究

嵌入式实时开发是当今计算机应用研究的热点,该文结合模型驱动架构的系统无关模型和系统相关模型思想,提出了一种基于平台设计的快速开发嵌入式实时系统的方法:首先采用实时应用接口RTAI将嵌入式Linux改造成具有硬实时性能的实时操作系统平台;然后利用Matlab/Simulink/RTW和RTAI-Lab工具对实际系统进行快速化建模、仿真和驱动开发,并自动生成实时的可执行代码;最后将代码加载到嵌入式实时系统.通过倒立摆嵌入式实时控制器系统设计实例说明了这种方法可以有效降低系统设计复杂度,提高嵌入式软件的开发效率.     

TEFL:一种文本式特征建模语言

特征模型已经成为软件产品线工程中共性/可变性建模的事实标准.现有基于特征图的建模工具由于在模型表达能力、严谨的形式化语义等方面的不足限制了其在工业界的应用.为了消除这些建模中的缺陷,为基于特征的产品线开发提供一个坚实的支撑环境,提出文本式特征建模语言TEFL,介绍其具体语法、抽象语法,以及形式化语义;开发一个基于Eclipse的语言编辑器原型;给出了面向XML和Java语言应用转化方法和工具;分析了与现有文本式建模技术相比所具有的优势与不足,并指出在特征建模及其工具技术方面的进一步的工作方向.     

基于可扩展端口技术的实时领域分层递阶建模方法

在采用模型驱动的开发(MDD)方法对复杂实时系统进行建模设计时,单层的建模方法难以完成对控制系统的清晰和完整描述。针对上述问题提出了一种分层递阶机制的实时多层建模方法,该方法使用可扩展输入端口和输出端口对现有元模型技术进行扩展,采用可扩展标记语言(XML)实现端口的描述,利用基于信道的端口消息传递机制完成不同层模型之间通信。实际实时控制系统建模结果表明,与单层模型相比,分层递阶的建模方法能够有效实现模型驱动设计方法在实时领域内对并行多任务和复杂交互行为的描述,从而提高实时领域模型的可读性和可复用性。     

Timed SEFM:面向嵌入式实时控制系统的编程模型

实时任务的功能和其完成时间共同影响嵌入式控制系统的物理行为。传统的进程/线程模型缺乏时间语义,时间属性只能用优先级间接表达,任务的实际完成时间不具有确定性。Henzinger提出的LET(Logical Execution Time)编程模型用协作式的时间触发语义明确描述时间需求,但其所基于的操作系统仍沿用进程/线程模型,仍会引入时间不确定性。结合服务体/执行流模型SEFM(Servant/Exe-Flow Model)和LET模型,定义了一种时间确定的编程模型Timed SEFM,用改进的SEFM模型描述系统的功能行为,用LET描述系统的时间行为。把智能小车控制系统的实现作为研究实例。     

XCY语言的静态指称语义的设计

本文讨论了用VDM元语言形式地描述XCY的静态指称语义.在引言中对研究表态语义的意义,所采用的方法进行了介绍.第二部分讨论了抽象语法的设计,从BNF描述的具体语法到VDM描述的抽象语法之间的变换,以及设计XCY语言的抽象语法中的一些考虑.第三部分描述了静态环境和模块指称的设计.第四部分讨论了静态环境和模块上的几个语义函数的构造.最后是结论.在附录中给出了XCY语言的静态指称语义(略).     

基于XYZ/E的混成系统

混成系统是由计算机和物理设备组成的嵌入式实时计算系统.它允许在交互式实时系统中引入连续变化的单元.XYZ/E 是基于Manna-Pnueli的线性时序逻辑的程序设计语言.它将程序的动态语义与静态语义统一在同一框架中,支持从抽象的程序规范到可执行代码的逐步求精的全过程.该文使用XYZ/E语言描述和验证混成系统.首先介绍了计算模型,然后介绍了XYZ语言对混成系统的形式化描述,最后介绍了混成系统的验证.与同类工作相比,XYZ/E支持状态转换,从而可以方便地描述复杂的控制算法.     

基于XML的UML模型向AADL模型的自动转换

UML已经成为复杂系统建模的工业标准,并可借助代码自动生成工具实现从分析到编码的开发过程自动化;AADL具有精确的语义和严格的语法规范,可用于描述嵌入式实时系统的软、硬件体系结构,并能分析系统的功能及非功能属性。 UML和AADL模型的基本元对象有相互对应关系,并且两种模型的表示都能够采用标准的XML的交换格式。为充分发挥两种语言的优势,文中研究了UML模型向AADL模型的自动转换,以XML为媒介实现两种模型的元对象的对应转换,最终达到两种模型的转换,使用户在设计阶段能够结合运用AADL、UML工具的优点对系统进行分析。     

SPIN语义引擎执行方式研究

模型检查工具SPIN的核心是PROMELA语言,对PROMELA语言执行方式的理解决定所描述系统模型的行为方式。本文从语义角度研究PROMELA语义引擎问题,首先给出PROMELA语法的抽象对象模型形式化定义,然后给出一个算法来实现PROMELA语法到抽象对象模型的映射,描述PROMELA指称语义。最后针对SPIN中atomic序列和同步通信等复杂问题给出解决方法。     

Windows设备驱动程序的实时内核设计

针对工业控制领域中对Windows操作系统的实时性需求,提出在Windows驱动程序中设计实时内核并进行任务调度的方法.着重研究了Windows驱动实时系统的实现方案和系统结构以及实时内核的任务调度设计和任务切换过程,完成了Window s驱动实时系统的设计与开发工作.通过对所设计系统的测试,验证了系统具有较好的实时性能,能满足一般工业控制场合的需求.     

一种新型的构件化操作系统的内核设计

采用构件化模型是当前操作系统设计新的发展趋势.构件化操作系统设计的关键技术集中反映在其内核的设计与实现中.本文首先介绍已有的内核结构以及操作系统新的抽象--服务体/执行流模型(SEFM),进而介绍基于SEFM的构件化操作系统Minicore中内核(核心服务体)的设计技术.最后以实际的测试数据验证了所采用技术的有效性.     

Program Behavior at the Symbolic Level

No application programmer writes machine-language programs–i.e., strings of ones and zeroes. That primitive pursuit has long been reserved for those few who create the very first modules of a software system for new hardware. Instead, programmers make use of a wide spectrum of symbolic programming languages, ranging from assembly code to high-level languages such as Fortran, Cobol, and the Algol family. Every programming language has semantics which define some abstract machine. For the assembly-language programmer this machine bears a great resemblance to the actual hardware on which the program will be interpreted, but even here the programmer will frequently use system-defined subroutines or macros which represent extensions of the base hardware facilities. The high-level language programmer's abstract machine reflects the control mechanisms and data structures characteristic of the language. The Fortran programmer, for example, can think in terms of multidimensional array structures, DO loops, subprogram facilities, and so on. In principle he need never be concerned with the manner in which his abstract Fortran machine is to be realized by a particular hardware and software system. The user of a modern electronic hand calculator needs no knowledge of the works inside the box, and a modern high-level language system should present to its users an equally consistent environment, completely defined in terms of the syntax and semantics of the source language.     

AspectualACME语言切点指示器的形式化描述方法

面向方面软件体系结构描述语言AspectualACME虽引入了切点指示器PCD(Pointcut Designator)的语法成分,但仍未给出其语义的形式化描述。针对这一问题,基于AspectualACME语言抽象语法树,设计了一阶逻辑语言LIAPCD(Logic Language forPCD)。在此基础上提出了AspectualACME语言PCD的形式化描述方法。该方法能精确定义软件体系结构层PCD的语义,可为形式化分析软件体系结构层方面编织提供支持。     

嵌入式系统软硬件协同验证中软件验证方法

随着集成电路及计算机技术的发展，嵌入式系统设计变得越来越复杂．复杂的嵌入式系统设计，通常采用验证的手段检验系统设计的正确性，硬件验证通常是在硬件设计描述的基础上建立用于模拟硬件功能的硬件模拟器；软件验证常用的方法是建立处理器功能模型(指令集模拟器ISS)，逐条解释嵌入式软件在目标机器上的执行过程，产生模拟输出，驱动外围电路(即硬件设计)．指令集模拟器从底层时序关系模拟嵌入式软件在目标CPU上运行过程．对于复杂嵌入式系统设计，ISS模拟速度通常成为协同模拟瓶颈．基于RTOS的嵌入式软件快速验证方法可以有效地提高软件模拟速度，扩展RTOS功能，适应协同模拟需要，建立硬件模拟驱动，实现软件和硬件模拟器通信连接和协同模拟同步控制．基于RTOS的嵌入式软件验证方法以编译代码模型为基础，从系统行为级验证嵌入式软件功能，验证速度快．在实际应用中，该方法和ISS验证相结合，能够实现更有效、更快速的嵌入式系统协同验证．最后以几个典型硬件设计为基础，编写相应的控制软件，进行软硬件协同验证实验，实验结果数据说明该验证方法实用、有效、快速．     

Named graphs

The Semantic Web consists of many RDF graphs nameable by URIs. This paper extends the syntax and semantics of RDF to cover such named graphs. This enables RDF statements that describe graphs, which is beneficial in many Semantic Web application areas. Named graphs are given an abstract syntax, a formal semantics, an XML syntax, and a syntax based on N3. SPARQL is a query language applicable to named graphs. A specific application area discussed in detail is that of describing provenance information. This paper provides a formally defined framework suited to being a foundation for the Semantic Web trust layer.     

Performance modelling of a network processor using POOSL

The increasing complexity of innovative real-time hardware/software systems forced industry to consider system-level design methods. Before actually implementing a system with hardware and software components, system-level design methods enable analysing the performance of different design alternatives that realise the required functionality. In order to develop performance models early in the design process, the parallel object-oriented specification language (POOSL) can be used. POOSL is an expressive modelling language for analysing complex real-time distributed hardware/software systems. Being equipped with a formal semantics, POOSL ensures unambiguous execution of models and proper application of performance analysis techniques. This paper discusses the use of POOSL for analysing the performance of a network processor. A network processor consists of components that perform their behaviour in a synchronously concurrent way, whereas POOSL is based on an asynchronous modelling paradigm. In this paper, we illustrate that constructing abstract models of synchronous systems for the purpose of performance analysis may benefit from an asynchronous modelling approach.     

SLAN-4?A Software Specification and Design Language

SLAN-4 (``Software Language-4') was developed to meet the need for a formal tool for specifying and designing large software systems. It provides language constructs for algebraic and axiomatic specifications and also pseudocode constructs for the design step. A major design goal was to ease subsequent refinements of a (given) specification. The design can start with a very informal specification, which can be implemented later using lower level concepts. This paper gives an overview of the SLAN-4 syntax and semantics. It concentrates on the most important aspects of: ? abstract data types, ? algebraic specification of abstract data types, and ? axiomatic specification of modules. Because the pseudocode part of SLAN-4 consists mainly of control structures similar to those in modern high-level programming languages, this element of the language is not separately described. The paper includes an example of how to use SLAN-4, and also the experiences gained in using the language to formally specify a real-world software product of about 18 000 lines of code written in an IBM internal high-level language.     

An institution theory of formal meta-modelling in graphically extended BNF

Meta-modelling plays an important role in model driven software development.In this paper,a graphic extension of BNF (GEBNF) is proposed to define the abstract syntax of graphic modelling languages.Fro...