816实用软件工程

1、软 件 工 程软件工程软件工程 齐治昌齐治昌高等教育出版社（高等教育出版社（1997）教教 材材软 件 工 程软件工程导论（第三版）软件工程导论（第三版） 张海藩张海藩 清华大学出版社（清华大学出版社（1997）参考书目参考书目软 件 工 程 实用软件工程实用软件工程 （第二版）（第二版） 郑人杰郑人杰 殷人昆殷人昆 陶永雷陶永雷 清华大清华大学出版社（学出版社（1996） 软件工程软件工程 -实践者的研究方法实践者的研究方法（英文版（英文版 第四版）第四版） roger s. pressman 机械工业出版社机械工业出版社参考书目参考书目 fundamentals of software e

2、ngineering carlo ghezzi, mehdi jazayeri, dino mandrioli prentice-hall, inc. (1991) software engineering , theory and practice shari lawrence pfleeger , prentice-hall, inc.(1998) 软件工程 近二十年来计算机软件已经成为现代科学研究和解决工程问题的基础，以及管理部门、生产部门、和服务行业中的关键因素，渗透到了各个领域，成为当今世界不可缺少的一部分。 展望二十一世纪，软件仍将成为驱动任何事情从基础教育到遗传工程取得新进展的动

3、力。 学习研究工程化的软件开发方法，使开发过程更加规范。 f为具体运用专门编写小规模的程序f软件作坊的出现沿用个体软件开发方法使得软件不可维护f出现软件危机分布式系统、计算机网络、嵌入式系统发展面向对象、专家系统、人工智能的应用（software crisis)例例: : 美国美国ibmibm公司在公司在19631963年至年至19661966年开发的年开发的ibm360ibm360机的操作系统。这一项目花了机的操作系统。这一项目花了50005000人一人一年的工作量，最多时有年的工作量，最多时有10001000人投入开发工作，人投入开发工作，写出了近写出了近100100万行源程序。万行源程序

4、。.据统计，这个据统计，这个操作系统每次发行的新版本都是从前一版本中操作系统每次发行的新版本都是从前一版本中找出找出10001000个程序错误而修正的结果。个程序错误而修正的结果。 . 这个项目的负责人这个项目的负责人f. d. brooksf. d. brooks事后总结了他在组织开事后总结了他在组织开发过程中的沉痛教训时说：发过程中的沉痛教训时说：“.正像一只逃亡的野兽落正像一只逃亡的野兽落到泥潭中做垂死的挣扎，越是挣扎，陷得越深，最后无法逃到泥潭中做垂死的挣扎，越是挣扎，陷得越深，最后无法逃脱灭顶的灾难。脱灭顶的灾难。.程序设计工作正像这样一个泥程序设计工作正像这样一个泥潭，潭，.一批批

5、程序员被迫在泥潭中拼命挣扎，一批批程序员被迫在泥潭中拼命挣扎，.谁谁也没有料到问题竟会陷入这样的困境也没有料到问题竟会陷入这样的困境.”.”。ibm360ibm360操作操作系统的历史教训成为软件开发项目的典型事例为人们所记取。系统的历史教训成为软件开发项目的典型事例为人们所记取。software crisis ! 项目没有被很好地理解；计划不周，最终导致进度拖项目没有被很好地理解；计划不周，最终导致进度拖延。延。例例1. in the late 1960s, a bright-eyed young engineer* was chosen to “write” a computer prog

6、ram for an automated manufacturing application. the reason for his selection was simple. he was the only person in his technical group who had attended a computer programming seminar. he knew the ins and outs of assembler language and fortran, but nothing about software engineering and even less abo

7、ut project scheduling and tracking.*if youre wondering whether this story is autobiographical, it is!问题出在哪里？问题出在哪里？his boss gave him the appropriate manuals and a verbal description of what had to be done. he was informed that the project must be completed in two months.he read the manuals, consider

8、ed his approach, and began writing code. after two weeks, the boss called him into his office and asked how things were going.“really great,” said the young engineer with youthful enthusiasm, “this was much simpler than i thought. im probably close to 75 percent finished.”the boss smiled. “thats rea

9、lly terrific,” he said. he then told the young engineer to keep up the good work and plan to meet again in a weeks time.a week later the boss called the engineer into his office and asked, “where are we?”“everythings going well,” said the youngster, “but ive run into a few small snags. ill get them

10、ironed out and be back on track soon.”“how does the deadline look?” the boss asked.“no problem,” said the engineer. “im close to 90 percent complete.”if youve been working in the software world for more than a few years, you can finish the story. itll come as no surprise that the young engineer stay

11、ed 90 percent complete for the entire project duration and only finished (with the help of others) one month late.例例2： in the early 1980s, the united states internal revenue service (irs) hired sperry corporation to build an automated federal income tax form processing system. according to the washi

12、ngton post, the “system has proved inadequate to the workload, cost nearly twice what was expected and must be replaced soon” (sawyer 1985). in 1985, an extra $90 million was needed to enhance the original $103 million worth of sperry equipment. in addition, because the problem prevented the irs fro

13、m returning refunds to taxpayers by the deadline, the irs was forced to pay $40.2 million in interest and $22.3 million in overtime wages for its employees who were trying to catch up. in 1996, the situation had not improved. the los angeles times reported on march 29 that there was still no master

14、plan for the modernization of irs computers, only a six-thousand-page technical document. congressman jim lightfoot called the project “a $4-billion fiasco that is floundering because of inadequate planning” (vartabedian 1996).myth: if we get behind schedule, we can add more programmers and catch up

15、.reality: software development is not a mechanistic process like manufacturing. in the words of brooks, “adding people to a late software project makes it later.” 没有充分的文档资料没有充分的文档资料(documentation) myth: the only deliverable for a successful project is the working program.reality: a working program i

16、s only one part of a software configuration that includes programs, documents, and data. documentation forms the foundation for successful development and, more important, provides guidance for the software maintenance task.vital!人与人的人与人的交流交流比写程序困难得多。比写程序困难得多。managers evaluate, track progress, .prog

17、rammers communicate to each othermaintainers 软件可靠性软件可靠性(reliability)(reliability)缺少度量的标准，质量无缺少度量的标准，质量无法保证。法保证。 如何保证软件产品的质量，是非常复杂困难的问如何保证软件产品的质量，是非常复杂困难的问题。特别对于规模庞大的软件，如：题。特别对于规模庞大的软件，如：.the software supporting the american space shuttle consists of 3 million lines of code, including computers on th

18、e ground controlling the launch and the flight; there were one hundred thousand lines of code in the shuttle itself in 1985.president reagans proposed strategic defense initiative (sdi) is estimated to require 10 to 100 million lines of code. many computer scientists and software engineers continue to believe there is no way to write and test the software to guarantee adequate reliability. 软件难以维护软件难以维护(maintainability) (maintainability) 不易升级不易升级(evolvability)(evolvability)myth: once we write the program and get it to work, our job