Teal Tractors Mini Case(小型案例)Study 美国的Teal拖拉机销售公司开发了一个信息系统，可处理 所有业务问题。后来，它收购了加拿大的拖拉机公司，准备 把业务扩展到加拿大。 Requirements change:from USA to Canada Changes include: Additional sales regions must be added must be able to handle Canadian taxes and other business aspects be extended to handle two different currencies,USD and CAD Changes may be Great for the company;but -Disastrous(灾难)for the information system
Slide 2.16 16/50 Teal Tractors Mini Case(小型案例) Study 美国的 Teal 拖拉机销售公司开发了一个信息系统，可处理 所有业务问题。后来，它收购了加拿大的拖拉机公司，准备 把业务扩展到加拿大。 Requirements change: from USA to Canada Changes include: – Additional sales regions must be added – must be able to handle Canadian taxes and other business aspects – be extended to handle two different currencies, USD and CAD Changes may be – Great for the company; but – Disastrous(灾难) for the information system
Moving Target Problem(移动目标问题) Information system -regression fault(回归错误)：fault in unrelated part of the system -Redesigned(重新设计)and reimplemented(重新开发) Change is inevitable Growing companies are always going to change No solution to the moving target problem
Slide 2.17 17/50 Moving Target Problem (移动目标问题) Information system – regression fault (回归错误): fault in unrelated part of the system – Redesigned(重新设计) and reimplemented (重新开发) Change is inevitable – Growing companies are always going to change – No solution to the moving target problem
Chapter Overview Information System Development in Theory理论上的信息系统开发 Winburg Mini Case Study一个小型案例研究 Lessons of the Winburg Mini Case Study这个小型案例研究的教训 Teal Tractors Mini Case Study第二个小型案例研究 Iteration and Incrementation迭代和增量 Iteration:The Newton-Raphson Algorithm迭代：牛顿拉普森算法 The Winburg Mini Case Study Revisited再次探讨第二个小型案例 Other Aspects of Iteration and Incrementation迭代和增量的其他方面 Managing Iteration and Incrementation管理迭代和增量 Maintenance Revisited再论维护
Slide 2.18 18/50 Chapter Overview Information System Development in Theory 理论上的信息系统开发 Winburg Mini Case Study 一个小型案例研究 Lessons of the Winburg Mini Case Study 这个小型案例研究的教训 Teal Tractors Mini Case Study 第二个小型案例研究 Iteration and Incrementation 迭代和增量 Iteration: The Newton–Raphson Algorithm 迭代: 牛顿-拉普森算法 The Winburg Mini Case Study Revisited 再次探讨第二个小型案例 Other Aspects of Iteration and Incrementation 迭代和增量的其他方面 Managing Iteration and Incrementation 管理迭代和增量 Maintenance Revisited 再论维护
Iteration(迭代)and Incrementation(增量) iterative:repeat -Each successive(后续的)version is closer to its target than its predecessor(前一个版本) Miller's Law:At any one time,we can concentrate on only approximately 7 chunks (信息单元) To handle larger amounts of information,use stepwise refinement(逐步求精法) Concentrate(关注)on the most aspects Postpone less critical aspects incremental process(增量过程)：increase
Slide 2.19 19/50 Iteration(迭代) and Incrementation(增量) iterative: repeat – Each successive(后续的) version is closer to its target than its predecessor(前一个版本) Miller’s Law: At any one time, we can concentrate on only approximately 7 chunks (信息单元) To handle larger amounts of information, use stepwise refinement (逐步求精法) – Concentrate(关注) on the most aspects – Postpone less critical aspects – incremental process(增量过程): increase
Version Version Version Version 1 2 3 4 (a) 4 2 (b) (a)Iteration (b)incrementation 两者经常联合使用
Slide 2.20 20/50 Iteration and Incrementation (a) Iteration (b) incrementation 两者经常联合使用