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论文:论软件可靠性设计与应用

目前在企业中,以软件为核心的产品得到了广泛的应用。随着系统中软件部分比例的不断增加,使得系统对软件的依赖性越来越强,对软件的可靠性要求也越来越高。软件可靠性与其他质量属性一样,是衡量软件架构的重要指标。

软件工程中已有很多比较成熟的设计技术,如结构化设计、模块化设计、自顶向下设计等,这些技术为保障软件的整体质量发挥了重要作用。在此基础上,为了进一步提高软件的可靠性,通常会采用一些特殊的设计技术,即软件可靠性设计技术。

在软件可靠性工程体系中,包含有可靠性模型与预测、可靠性设计和可靠性测试方法等。实践证明,保障软件可靠性最有效、最经济、最重要的手段是在软件设计阶段采取措施进行可靠性控制。

请围绕“软件可靠性设计与应用”论题,分别从以下三个方面进行论述。

1.概要叙述你参与实施的软件开发项目以及你所承担的主要工作。

2.简要叙述影响软件可靠性的因素有哪些。

3.阐述常用的软件可靠性设计技术以及你如何应用到实际项目中,效果如何。

答案

参考答案:

写作要点

1.论文中要具体介绍项目的总体需求(特别是可靠性需求)、采用的技术等内容和承担的实际工作。

2.影响软件可靠性的主要因素有:运行环境(软件可靠性的定义是相对于运行环境的):软件规模;软件内部结构(内部结构越复杂,包含的缺陷数就可能越多);软件的开发方法和开发环境;软件的可靠性投入等。

3.可靠性设计是在常规的软件设计中,应用各种方法和技术使程序设计在兼顾用户功能和性能需求的同时,全面满足软件的可靠性要求。软件可靠性设计技术就是以提高和保障软件的可靠性为目的,在软件设计阶段运用的一种特殊的设计技术。

主要的软件可靠性设计技术包括:

(1)容错设计技术。对于软件失效后果特别严重的场合,例如宇航器控制系统、空中交通控制和核反应堆控制系统等,可采用容错设计方法。常用的软件容错技术主要有恢复块设计、N版本程序设计和冗余设计。恢复块设计就是选择一组操作作为容错设计单元,从而把普通的程序块变为恢复块。一个恢复块中包含有若干功能相同、设计差异的程序块,每一时刻有一个程序块处于运行状态,一旦某程序块出现故障,则用备份程序块予以替换。N版本程序设计的核心是通过设计出多个模块或不同版本,对于相同初始条件和相同输入的操作结果进行多数表决(防止因其中某一软件模块/版本的故障而提供了错误的服务,以实现软件容错)。冗余设计的思路来源于硬件系统,但有所不同。软件冗余设计技术是采用多种不同路径、不同算法或不同实现方法的模块或系统作为备份,在出现故障时进行替换,维持系统的正常运行。

(2)检测技术。在无须在线容错或不能采用冗余设计技术的部分,但又有较高的可靠性要求时,一般采用检测性设计,在软件出现故障后能及时发现并报警。但其明显的缺点是不能自动解决故障,如果没有人工干预,最终将导致系统不能正常运行。

(3)降低复杂度设计。软件的复杂性与软件可靠性有密切关系。软件复杂性是产生软件缺陷的重要根源。降低复杂度设计的思想就是在保证实现软件功能基础上,简化软件结构。

阅读理解

阅读理解。

     From bankers to factory staff, employees in the West face a cold "prospect" of losing

their jobs as a global recession(衰退) starts to bite. For colleagues in the East, the pain is more

likely to come through a pay cut.

     Human resource experts say cultural differences explain why Asian companies try harder to

preserve jobs in difficult times, which will prevent unemployment and may help Asian economies

survive at a time of slowing exports. The East Asian attitude may also make it easier for companies

to recover quickly from the economic downturn since they will not need to rehire or train new staff,

but build up a more loyal and devoted group.

     "In the Confucian mindset(儒家思想), the right thing to do is to share the burden, which is the

sense of collective(集体的)responsibility. While in the West, it's more about individual survival,"

said Michael Benoliel, associate professor of organizational behavior at Singapore Management

University (SMU).

     In contrast, local Western companies from General Motors to Goldman Sachs plan to lay off

workers by the thousands, but at the Asian units of Western multinationals or western units of Asian

groups, job cuts will probably be less severe.

     Japan's jobless rate was 4 percent in September, up from 3.8 percent in January, while Hong

Kong's was flat at 3.4 percent. But US unemployment is expected to have jumped to 6.3 percent

last month from below 5 percent in January.

     Experts say that while there are noticeable differences in labor practices in East and West, the

gap will narrow as more firms become more multinational and competition forces firms to adopt the

best practices of rivals from abroad.

1. The underlined word "prospect" in the first paragraph most probably means _________.

A. weather    

B. scene    

C. future    

D. place

2. Compared with job cuts, pay cuts can bring the following benefits EXCEPT that _________.

A. it's helpful to the economy recovery

B. it costs the company less money to survive

C. it will keep the experienced and skilled workers

D. it can form a team working harder and more loyally

3. According to Michael Benoliel, the Confucian mindset focuses on _________.

A. human rights                

B. sharing responsibility

C. personal profits              

D. individual survival

4. In which company can we infer the job cuts will be probably the most severe?

A. A local American group.

B. A small Japanese company.

C. A German branch of a Korean multinational.

D. A Hong Kong's unit of a French company.

5. The passage mainly tells us ________.

A. the difficulties all the companies around the world will meet with today

B. the cultural differences between Eastern and Western world at present

C. the ways to cut down the cost of the companies in economic downturn

D. the different labor solutions of Asian and Western in global recession

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