chapter5.ppt

DataBase System Concepts
Chapter 5
Database Design and the E_R Model
DataBase System Concepts
Content:
Database Schema;
logical schema, physical schema
Application system;
Technology, Running , Data
DataBase System Concepts
Software Engineering
Software engineering is the discipline concerned with the application of theory, knowledge, and practice for effectively and efficiently building software system that satisfy the requirements of users and customers.
. is applicable to small, medium, and large-scale systems. It passes all phases of the life cycle of a software system.
Software Engineering is the establishment & use of sound engineering principles in order to obtain economically software that is reliable & work efficiently on real machines
--- Fritz Bauer, 1969, NATO
DataBase System Concepts
建立并使用完善的工程化原则,以较经济的手段获得能在实际机器上有效运行的可靠软件的一种方法。
DataBase System Concepts
Software + Documents
DataBase System Concepts
DataBase System Concepts
Why Software Projects Fail
Factors %
1. plete Requirements %
2. Lack of User Involvement %
3. Lack of Resources %
4. Unrealistic Expectations %
5. Lack of Executive Support %
6. Changing Requirements & Specifications %
7. Lack of Planning %
8. Didn‘t Need It Any Longer %
9. Lack of IT Management %
10. Technology Illiteracy %
11. Others %
Source: Standish Group 1995
DataBase System Concepts
Waterfall approach: Development cycle is divided into phases such as requirements specification, software design, implementation, testing, operation and maintenance. Software project is developed stage by stage.
Evolutionary development: This approach interleaves the activities of specification, design and implementation; and validation. In accordance with the customer input, an initial system can be rapidly developed from very abstract specifications, . rapid prototyping.
Formal transformation: This approach is based on producing a formal mathematical system specification so that