1. 6 Chapter 6 Database Design Hachim Haddouti

2. 6 2 Hachim Haddouti and Rob & Coronel, Ch6 In this chapter, you will learn: That successful database design must reflect the information system of which the database is a part That successful information systems/ databases are subject to frequent evaluation and revision within a framework known as the Systems Development Life Cycle (SDLC), and Database Life Cycle (DBLC) resp How to conduct evaluation and revision within the SDLC and DBLC frameworks top-down vs. bottom-up design and centralized vs. decentralized design

3. 6 3 Hachim Haddouti and Rob & Coronel, Ch6 Data –Raw facts stored in databases –Need additional processing to become useful Information –Required by decision maker –Data processed and presented in a meaningful form –Transformation Changing Data into Information

4. 6 4 Hachim Haddouti and Rob & Coronel, Ch6 Database –Carefully designed and constructed repository of facts –Part of an information system Information System –Provides data collection, storage, and retrieval –Facilitates data transformation –Components include: People Hardware Software – Database(s) – Application programs – Procedures The Information System

5. 6 5 Hachim Haddouti and Rob & Coronel, Ch6 System Analysis –Establishes need and extent of an information system Systems development –Process of creating information system Database development –Process of database design and implementation –Creation of database models –Implementation Creating storage structure Loading data into database Providing for data management The Information System (Con’t.)

6. 6 6 Hachim Haddouti and Rob & Coronel, Ch6 Systems Development Life Cycle GO/ NO GO GO/ NO GO

7. 6 7 Hachim Haddouti and Rob & Coronel, Ch6 Database Lifecycle (DBLC)

8. 6 8 Hachim Haddouti and Rob & Coronel, Ch6 Phase 1: Database Initial Study Purposes –Analyze company situation Operating environment Organizational structure –Define problems and constraints –Define objectives –Define scope and boundaries (size f ballpark)

9. 6 9 Hachim Haddouti and Rob & Coronel, Ch6 Initial Study Activities

10. 6 10 Hachim Haddouti and Rob & Coronel, Ch6 Phase 2: Database Design Most Critical DBLC phase Makes sure final product meets requirements Focus on data requirements Subphases –Create conceptual design –DBMS software selection –Create logical design –Create physical design

11. 6 11 Hachim Haddouti and Rob & Coronel, Ch6 Two Views of Data

12. 6 12 Hachim Haddouti and Rob & Coronel, Ch6 I. Conceptual Design Data modeling creates abstract data structure to represent real-world items High level of abstraction Four steps –Data analysis and requirements –Entity relationship modeling and normalization –Data model verification –Distributed database design

13. 6 13 Hachim Haddouti and Rob & Coronel, Ch6 Data analysis and Requirements Focus on: –Information needs –Information users –Information sources –Information constitution Data sources –Developing and gathering end-user data views –Direct observation of current system –Interfacing with systems design group Business rules (connectivities, cardinalities, entities, attributes, relationships, constraints)

14. 6 14 Hachim Haddouti and Rob & Coronel, Ch6 Entity Relationship Modeling and Normalization

15. 6 15 Hachim Haddouti and Rob & Coronel, Ch6 E-R Modeling is Iterative

16. 6 16 Hachim Haddouti and Rob & Coronel, Ch6 Concept Design: Tools and Sources

17. 6 17 Hachim Haddouti and Rob & Coronel, Ch6 Data Model Verification E-R model is verified against proposed system processes –End user views and required transactions –Access paths, security, concurrency control –Business-imposed data requirements and constraints Reveals additional entity and attribute details Processes classified according to frequencies or operational types

18. 6 18 Hachim Haddouti and Rob & Coronel, Ch6 E-R Model Verification Process

19. 6 19 Hachim Haddouti and Rob & Coronel, Ch6 Iterative Process of Verification

20. 6 20 Hachim Haddouti and Rob & Coronel, Ch6 Distributed Database Design Design portions in different physical locations Development of data distribution and allocation strategies

21. 6 21 Hachim Haddouti and Rob & Coronel, Ch6 II. DBMS Software Selection DBMS software selection is critical Advantages and disadvantages need study Factors affecting purchasing decision –Cost –DBMS features and tools –Underlying model –Portability –DBMS hardware requirements

22. 6 22 Hachim Haddouti and Rob & Coronel, Ch6 III. Logical Design Translates conceptual design into internal model Maps objects in model to specific DBMS constructs Design components –Tables –Indexes –Views –Transactions –Access authorities –Others

23. 6 23 Hachim Haddouti and Rob & Coronel, Ch6 IV. Physical Design Selection of data storage and access characteristics –Very technical –More important in older hierarchical and network models Becomes more complex for distributed systems Designers favor software that hides physical details

24. 6 24 Hachim Haddouti and Rob & Coronel, Ch6 Physical Organization

25. 6 25 Hachim Haddouti and Rob & Coronel, Ch6 Phase 3: Implementation and Loading Creation of special storage-related constructs to house end-user tables Data loaded into tables Other issues –Performance –Security –Backup and recovery –Integrity –Company standards –Concurrency controls

26. 6 26 Hachim Haddouti and Rob & Coronel, Ch6 Phase 4: Testing and Evaluation Database is tested and fine-tuned for performance, integrity, concurrent access, and security constraints Done in parallel with application programming Actions taken if tests fail –Fine-tuning based on reference manuals –Modification of physical design –Modification of logical design –Upgrade or change DBMS software or hardware

27. 6 27 Hachim Haddouti and Rob & Coronel, Ch6 Phase 5: Operation Database considered operational Starts process of system evaluation Unforeseen problems may surface Demand for change is constant

28. 6 28 Hachim Haddouti and Rob & Coronel, Ch6 Phase 6: Maintenance and Evaluation Preventative maintenance Corrective maintenance Adaptive maintenance Assignment of access permissions Generation of database access statistics to monitor performance Periodic security audits based on system- generated statistics Periodic system usage-summaries

29. 6 29 Hachim Haddouti and Rob & Coronel, Ch6 DB Design Strategy Notes Top-down –1) Identify data sets –2) Define data elements Bottom-up –1) Identify data elements –2) Group them into data sets

30. 6 30 Hachim Haddouti and Rob & Coronel, Ch6 Top-Down vs. Bottom-Up Figure 6.14

31. 6 31 Hachim Haddouti and Rob & Coronel, Ch6 Centralized vs. Decentralized Design Centralized design –Typical of simple databases –Conducted by single person or small team Decentralized design –Larger numbers of entities and complex relations –Spread across multiple sites –Developed by teams

32. 6 32 Hachim Haddouti and Rob & Coronel, Ch6 Decentralized Design