软件工程大题含解答精华版

Exam 1 Practical - Solutions

1. List two of the factors that contributed to the \development, and explain how software engineering life-cycle approaches attempt to address those

factors.列出软件开发早期的导致“软件危机”的因素，并解释软件工程生命周期试图解决这些因素的方法 Many answers are possible. For example: high cost of maintenance addressed by better documentation, better design for understandability and extensibility, formal reviews, testing procedures, etc; high cost of development addressed by more emphasis on analysis and design before implementation begins; etc.(维护成本高解决办法为更好的文案，对于可理解性，可扩展性更好的设计，正式的评审，测试程序等;开发成本高解决办法为在实现开始前进行更全面的分析与设计)

2. What software life-cycle model would you use if there is significant technical risk and the customer's requirements are not well-known in advance? Justify your answer in a short essay.(如果有重大技术风险和客户的要求是不明确的，你会使用什么软件生命周期模型？在一篇短文中证明你的答案) Either spiral or rapid prototyping, or a combination of both. Spiral has good risk management characteristics, and can be implemented to include early prototypes or simulations to show to the customer. Rapid prototyping is good for clarifying requirements with the customer, and can be used to put early pressure on components with technical risk.（无论是螺旋模型或快速原型模型，还是两者的结合都可以。螺旋模型具有良好的风险管理特性，可以实现早期原型或模拟显示给客户。快速原型技术有助于明确客户的真正需求，减少由

于软件需求不明确带来的开发风险）

3. The engineers at hypothetical.com adopted the incremental model for the development of their intelligent Web-based search agent. After implementing version 1.0 (which supported basic keyword searching of a list of sites using keyword query) they found that they could not implement version 2.0 (which supports searching using Boolean combinations of keywords) without completely re-designing the query module. Why do you think this problem might have arisen? Suggest two ways that the problem might have been avoided. Justify your answer in a short essay.(工程师们在hypothetical.com工程采用增量模型用于他们的基于网络的智能搜索代理的开发。在实现1.0版本（支持基本的关键字搜索的网站，使用关键字查询），他们发现，他们无法实现2版本（支持搜索使用布尔组合的关键字）没有完全重新设计的查询模块。你为什么认为这个问题会出现？给出2种该问题可能被避免的方法。在一篇短文中证明你的答案。) The problem was probably caused by a lack of detail in the requirements analysis phase, a lack of detail in the design phase, or some combination of both. More attention to detail in these areas could have remedied the problem, assuming that all of the basic functional requirements were known in advance. If the requirements were underspecified and/or not completely known, then a better choice of development model might have been the rapid prototyping model or spiral model. Or, the incremental could have been used after an initial rapid prototype was used as a technique for firming up the requirements.(这个问题很可能是在需求分析阶段缺少细节或者在设计阶段缺乏细节，或者是两者的结合。如果在分析，设计阶段，考虑到更多的细节，或许可以纠正这个问题，假设所有的基本功能要求已知。如果要求是未指定的，或着是不完全清楚的，那么开发模式更好的选择可以是快速原型模型、螺旋模型。或者，增量模型可以在经过最初的快速原型模型

之后，作为一个坚定的开发技术模型。)

4. Case Study: Consider an automated library circulation system.

o Every book has a bar code and every borrower has a card bearing a bar code.

o When a borrower wishes to check out a book, the librarian scans the bar code on the book and on

the borrower's card, and then enters C at the computer terminal.

o When a book is returned, it is again scanned and the librarian enters R. o Librarians can add books (+) to the library collection or remove them (-). o Borrowers can go to a terminal and determine:

? all the books in the library by a particular author

(the borrower types A= followed by the author's name) ? all the books with a specific title

(the borrower types T= followed by the title) ? all the books in a particular subject area

(the borrower types S= followed by the subject area)

o If a borrower wants a book that is currently checked out, the librarian can place a hold on the

book so that, when it is returned, it will be held for the borrower who requested it (the librarian types H= followed by the number of the book) Questions

7. Draw a dataflow diagram for the system, showing as much detail as you can without making

assumptions about implementation.

The dataflow diagram for the entire system is shown immediately below. The Process Command process is shown using a hierarchical expansion in the second diagram.

8. Draw a state transition diagram for the system.

NOTE about the diagram:

?

The diagram uses separate states for reading commands and bar codes to show the sequence in which the bar codes and commands are expected.

(状态变迁图使用单独的状态用于读取命令与条形码来显示条形码和命令的时序。)

9. Draw an entity-relationship diagram for the system.