1. 2 Copyright © 2006, Oracle. All rights reserved. Introduction to Database Development Chapter 2

2. 2- 2 Outline Context for database development Goals of database development Phases of database development CASE tools

3. 2- 3 Information System 現金收支 滯納通知 Environment

4. 2- 4 Traditional Life Cycle of System Development

5. 2- 5 Development Alternatives Criticism about traditional life cycle of S.D. Operational system is produced late Rush to begin implementation Requirements are difficult to capture Alternative methodologies Spiral approaches Rapid application development –Prototypes ( 雛型系統 ) may reduce risk

6. 2- 6 Graphical Models The graphical models of the followings should be produced in all development alternatives: Data model Data and relationships Process model Relationships among processes Environment interaction model Relationship between events and processes

7. 2- 7 Goals of Database Development Develop a common vocabulary Define data meaning Ensure data quality Provide efficient implementation

8. 2- 8 Develop a Common Vocabulary Diverse groups of users Difficult to obtain acceptance of a common vocabulary Compromise to find least objectionable solution ( 最不受反對的解答 ) Unify organization by establishing a common vocabulary

9. 2- 9 Define Meaning of Data Business rules support organizational policies Example : An order must precede a shipment Restrictiveness ( 嚴謹性 ) of business rules –Too restrictive: reject ( 排拒 ) valid business interactions (May force work-around solutions to handle exceptions) (Exception handling allows flexibility) –Too loose: allow erroneous business interactions (May allow incorrect data in a database)

10. 2- 10 Data Quality Poor data quality leads to poor decision making –Poor customer communication –Inventory shortages Cost-benefit tradeoff to achieve desired level of data quality Long-term effects of poor data quality

11. 2- 11 Data Quality Measures Completeness D/B represents all important parts of the IS Lack of ambiguity ( 缺乏模糊性 ) Each part of the D/B has only one meaning Timeliness Business changes posted to the D/B without delay Correctness D/B contains values preceived by users Consistency Different parts of the D/B do not conflict Reliability Failures or interferences do not corrupt D/B

12. 2- 12 Efficient Implementation Even if other design goals are met, a slow-performing database will not be used. Supersedes and respects ( 考量 ) other goals as possible An optimization problem –Maximize performance –Subject to constraints of data quality, data meaning, and resource usage Difficult problem: –Number of choices –Relationships among choices –DBMS specific

13. 2- 13 Database Development Phases Conceptual Data Modeling Logical Database Design Distributed Database Design Physical Database Design ERD Tables Distribution Schema Internal Schema, Populated D/B Data requirements ( 可移植的資料庫 )

14. 2- 14 Conceptual Data Modeling Information content of the database Entity relationship diagram (ERD) showing entity types and relationships Historically, DBMSs did not support many constraints. Diverse ( 多元的 ) formats for database requirements

15. 2- 15 Logical Database Design Refine conceptual design Convert ERD to table design Analyze design for excessive redundancies ( 累贅 ) Normalization: tool to reason about redundancies Add constraints to enforce business rules

16. 2- 16 Distributed Database Design Performance orientation, not information content orientation Decisions: location of data and processing –Allocate subsets of database to different sites –Replicate subsets of database to improve availability

17. 2- 17 Physical Database Design Performed at each independent database site Minimize response time without consuming excessive resources Tradeoffs: retrieval versus update Flexible designs versus specialized designs Decisions: indexes, data placement

18. 2- 18 Splitting Conceptual Design

19. 2- 19 Cross Checking ( 交叉檢查 ) Requirements

20. 2- 20 Design Skills in Phases Soft Qualitative subjective ( 主觀性的 ) People-oriented Hard Quantitative Objective Intensive data analysis ( 密集的資料分析 )

21. 2- 21 Features of CASE Tools Diagramming Documentation Analysis Prototyping

22. 2- 22 Classification of CASE Tools Front-end ( 前端 ) vs. Back-end ( 後端 ) –Front-end emphasize data modeling and logical analysis –Back-end emphasize code generation and physical design DBMS dependent vs. DBMS independent

23. 2- 23 Commercial CASE Tools PowerDesigner 10 Oracle Designer 10g Visual Studio.Net Enterprise Architect ERWin Data Modeler ER/Studio Visible Analyst

24. 2- 24 ER Assistant CASE tool distributed with the textbook Customized for this textbook: supports the ERD notation used in Chapters 5 and 6 Drawing tool Diagram checking Easy to use and powerful tool

25. 2- 25 Visio Professional Entry level version of Visual Studio.Net Enterprise Architect Excellent drawing tools Stencils ( 樣板 ) for database diagrams Glue ( 黏合 ) feature to retain connections Useful analysis tools Diagram layout Reverse engineering Data dictionary support

26. 2- 26 Summary Background for Chapters 5 to 8 Relationship to information systems development Goals of database development Darabase development phases CASE tool features