软件工程第9版部分习题答案Word格式.doc

1、1.3 What are the four important attributes that all professional software should have? Suggest four other attributes that may sometimes be significant.Answer:Four important attributes are maintainability, dependability, performance and usability. Other attributes that may be significant could be reu

2、sability （can it be reused in other applications）, distributability （can it be distributed over a network of processors）, portability （can it operate on multiple platforms e.g laptop and mobile platforms） and inter-operability （can it work with a wide range of other software systems）.Decompositions

3、of the 4 key attributes e.g. dependability decomposes to security, safety, availability, etc. is also a valid answer to this question.2.1Giving reasons for your answer based on the type of system being developed, suggest the most appropriate generic software process model that might be used as a bas

4、is for managing the development of the following systems: A system to control anti-lock braking in a car A virtual reality system to support software maintenance A university accounting system that replaces an existing system An interactive travel planning system that helps users plan journeys with

5、the lowest environmental impact1. Anti-lock braking system This is a safety-critical system so requires a lot of up-front analysis before implementation. It certainly needs a plan-driven approach to development with the requirements carefully analysed. A waterfall model is therefore the most appropr

6、iate approach to use, perhaps with formal transformations between the different development stages.2. Virtual reality system This is a system where the requirements will change and there will be an extensive user interface components. Incremental development with, perhaps, some UI prototyping is the

7、 most appropriate model. An agile process may be used.3. University accounting system This is a system whose requirements are fairly ell-known and which will be used in an environment in conjunction with lots of other stems such as a research grant management system. Therefore, a reuse-based proach

8、is likely to be appropriate for this.4. Interactive travel planning system System with a complex user interface but which must be stable and reliable. An incremental development approach is the most appropriate as the system requirements will change as real user experience with the system is gained.

9、2.4Suggest why it is important to make a distinction between developing the user requirements and developing system requirements in the requirements engineering process.There is a fundamental difference between the user and the system requirements that mean they should be considered separately.1. Th

10、e user requirements are intended to describe the systems functions and features from a user perspective and it is essential that users understand these requirements. They should be expressed in natural language and may not be expressed in great detail, to allow some implementation flexibility. The p

11、eople involved in the process must be able to understand the users environment and application domain.2. The system requirements are much more detailed than the user requirements and are intended to be a precise specification of the system that may be part of a system contract. They may also be used

12、 in situations where development is outsourced and the development team need a complete specification of what should be developed. The system requirements are developed after user requirements have been established.Excercises（Homework）: P1164.2，*4.44.2Discover ambiguities or omissions in the followi

13、ng statement of requirements for part of a ticket-issuing system:An automated ticket-issuing system sells rail tickets. Users select their destination and input a credit card and a personal identification number.The rail ticket is issued and their credit card account charged. When the user presses t

14、he start button, a menu display of potential destinations is activated, along with a message to the user to select a destination. Once a destination has been selected, users are requested to input their credit card.Its validity is checked and the user is then requested to input a personal identifier

15、. When the credit transaction has been validated, the ticket is issued.Ambiguities and omissions include:l Can a customer buy several tickets for the same destination together or must they be bought one at a time?l Can customers cancel a request if a mistake has been made?l How should the system res

16、pond if an invalid card is input?l What happens if customers try to put their card in before selecting a destination （as they would in ATM machines）?l Must the user press the start button again if they wish to buy another ticket to a different destination?l Should the system only sell tickets between the station where the machine is situated