软件工程课后习题答案第八版.docx

1、软件工程课后习题答案第八版软件工程课后习题: What are the differences between generic software product development and custom software development? Solution: The essential difference is that in generic software product development, the specification is owned by the product developer. For custom product development, the s

2、pecification is owned by the customer. Of course, there may be differences in development processes but this is not necessarily the case.重要区别为：在通用软件的开发过程中，详细说明（规格说明书）由产品开发者来制定，在定制软件产品开发过程中，详细说明（规格说明书）由客户来制定。 What are the four important attributes which all software products should have? Suggest four

3、 other attributes that may sometimes be significant. Solution: For important attributes are maintainability可维护性, dependability 可靠性, performance(efficiency)有效性 and usability可用性.Other attributes that may be significant could be reusability可复用性 (can it be reused in other applications), distributability

4、 可分发性(can it be distributed over a network of processors), portability可移植性 (can it operate on multiple platforms) and inter-operability互用性 (can it work with a wide range of other software systems). What is the difference between a software process model and a software process? Suggest two ways in wh

5、ich a software process model might be helpful in identifying possible process improvements. Solution:A software process is what actually goes on when software is developed. A software process model is an abstraction and simplification of a process. Process models can be used to help understand real

6、processes and to identify which aspects of these processes could be supported by CASE tools. 软件过程就是指在软件开发过程中所做的一些事情。软件过程模型是过程的抽象和简化。过程模型可用于帮助理解真正的过程，并可用于识别过程中的哪些方面可用CASE工具支持。 Giving reasons for your answer based on the type of system being developed, suggest the most appropriate generic software pro

7、cess model that might be used as a basis for managing the development of the follow systems:1) Anti-lock braking system 2) Virtual reality system3) University accounting system 4) Interactive timetable Solution:(a) Anti-lock braking system: Safety-critical 安全鉴定system so method based on formal transf

8、ormations with proofs of equivalence等价 between each stage. (b) Virtual reality system: System whose requirements cannot be predicted预知 in advance预先地 so exploratory programming model is appropriate. (c) University accounting system: System whose requirements should be stable because of existing syste

9、m therefore waterfall model is appropriate. (d) Interactive timetable交互式时间表: System with a complex user interface but which must be stable and reliable. Should be based on throw-away prototyping to find requirements then either incremental development or waterfall model. Why a software system that i

10、s used in a real world environment must change or become progressively(日益增多地) less useful? Solution:Systems must change because as they are installed in an environment the environment adapts to them and this adaptation naturally generates new/different system requirements. 这种适应自然生成新的系统需求Furthermore,

11、 the systems environment is dynamic and constantly generates new requirements as a consequence of changes to the business, business goals and business policies.商务的目标以及政治相关Unless the system is adapted to reflect these requirements, its facilities will become out-of-step with the facilities needed to

12、support the business and, hence, it will become less useful. Why a good programmers is not always be a good software managers? Solution:Management activities such as proposal writing, project planning and personal selection require a set of skill including presentation 表述能力and communication skills交流

13、的能力. Organizational skills组织能力 and the ability to communicate with other project team members. Programming skills are distinct from these, it is common that they lack human communication skills他们缺乏交流技巧是一个普遍的事实. So it does not follow that good programmers can re-orient their abilities to be good mana

14、gers.管理活动包括提出书面建议，项目规划和进度，人员选择和评价，项目监督和评审，和其他队友的交流能力等。程序设计者的任务就不是这些，他们不需要和人交流的能力，如果按照做好一个程序设计者的要求去做管理者的话，他肯定不是一个号的管理者。 Why the process of project planning is iterative and why a plan must be continually不断地 reviewed during a software project. Solution:Project planning can only be based on available i

15、nformation. At the beginning of a project, there are many uncertainties in the available information and some information about the project and the product may not be available. As the project develops, more and more information becomes available and uncertainties are resolved. The project plan ther

16、efore must be reviewed and updated regularly to reflect this changing information environment. 软件项目地规划取决于有用地信息。在项目进行期间不断产生新的信息，所以必须经常性的修改原有的计划。原本有用的信息可能会不再有用，而原本一些不确定的信息反而会变得有用。最初对象目本身的估算是实验性的，所以计划需要不断的修改。 Suggest who might be stakeholders in a university student records system.The stakeholders in a

17、 student records system include: University central administration including those responsible for registration, payment of fees, exams and assessment and graduation. 大学管理中心，包括报到，交纳学费，考试，作业和毕业等The students whose details are recorded in the system. 记录在这个系统中的学生University departmental administrators wh

18、o supply information to the system and use information from it. 大学部门管理者，需要提供和使用这些信息Academic staff that use information from the system. 使用系统信息的学院成员Data protection officers (local and national). 数据保护工作者Potential employers of students（who may require information from the system）. 潜在的学生中的雇佣者在学生记录系统中的参与

19、者包括：。学校管理中心包括负责学生注册，缴费，考试，评估，毕业事宜的相关人员。那些被记录具体信息的学生。把学生信息录入到系统并使用系统信息的学校部门人员。使用这些信息的学术人员。数据安全人员（本地和国家的）。潜在的雇用学生的人（或许需要用到这个系统里面的信息）7.3 For three of the viewpoints identified in the library system. LIBYSY, suggest three requirement that could be suggested by stakeholders associated with that viewpoint

20、.Solution:You can tackle this problem using a brainstorming approach. Obviously, there are many alternatives to the solutions suggested here. Note the printing conflict is deliberate.Viewpoint: Library managerRequirement: Access to the LIBSYS system shall be restricted to accredited users of the lib

21、rary.Requirement: The LIBSYS system shall provide a reporting facility that allows usage reports (who used the system, how often, what libraries were accessed) to be created and printed.Requirement: The LIBSYS system shall be configured so that only document printing on specific library servers is p

22、ermitted.Viewpoint: UsersRequirement: The LIBSYS system shall be accessible from any location, including locations away from the university campus.Requirement: It shall be possible to save LIBSYS queries, recall them and modify them for subsequent use.Requirement: The LIBSYS system shall allow docum

23、ents to be printed on user printers.Viewpoint: System managersRequirement: The restart time of the LIBSYS system after failure shall not exceed 5 minutes.Requirement: The LIBSYS system shall provide a backup facility for users personal workspaces.Requirement: The LIBSYS system shall be available for

24、 a range of platforms including Windows 2000, Windows XP and Mac OS X.7.4 The LIBSYS system has to include support for cataloguing new documents where the system catalog may be distributed across several machines. What are likely to be the most important types of non-function requirement associated

25、with the cataloguing facilities? Solution:Important non-functional attributes for the cataloging services might be: Availability (because the system may be required at any time) Security (because the books data base musnt be corrupted) Efficiency (because the system must respond quickly to each tran

26、saction)For the browsing services, usability is also very important as these services should be easy to use without extensive training. Discuss an example of a type of system where social and political factors might strongly influence the system requirement. Explain why these factors are important i

27、n your example. Solution:An example of a system where social and political factors influence system requirements is a system to manage the costs of public healthcare. Politicians are anxious both to control costs and to ensure that the best public image of the healthcare system is provided. There is

28、 a potential conflict in such a system between administrators who are driven by treatment costs and doctors who are (or should be) driven by treatment effectiveness. The requirements for the system might therefore embed particular policies which are included as a result of organizations factors (e.g

29、. ensure that administrators can vet treatment costs) rather than technical requirements.社会和政治因素影响系统需求的一个例子是管理成本和公共卫生保健的系统。政治家们对控制成本和确保提供最好的卫生保健系统都很关心。在这样一个系统中这本来就是一对潜在的矛盾，系统管理人员关心的治疗成本而医生们关心的治疗效果。此时系统需求可能要建立在特殊的包括一系列组织因素的政策上而不是技术需求。 11.1 Why it may be necessary to design the system architecture bef

30、ore the specification are written?Solution:The architecture may have to be designed before specifications are written to provide a means of structuring the specification and developing different sub-system specifications concurrently, to allow manufacture of hardware by sub-contractors and to provid

31、e a model for system costing. 体系结构设计过程输出了一个体系结构的设计文档，这样的设计文档包含了一系列图形化的系统模型描述和一些相关的描述文本。该文当描述了系统如何有子系统构成以及每个子系统如何有模块构成。11.4 Giving reasons for your answer, suggest an appropriate structural model for the following systems:1. an automated ticket-issuing system used by passengers at a railway station2.

32、 a computer-controlled video conferencing system that allows video, audio and computer data to be visible to several participants at the same time.3. a robot floor-cleaner that is intended to clean relatively clear spaces such as corridors, the cleaner must be able to sense walls and other sbstructions.Solution:Ticket issuing system . The most appropri