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Chapter 6

Chapter 6. Database Design Hachim Haddouti. In this chapter, you will learn:. That successful database design must reflect the information system of which the database is a part

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Chapter 6

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  1. Chapter 6 Database Design Hachim Haddouti

  2. 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 Hachim Haddouti and Rob & Coronel, Ch6

  3. Changing Data into Information • 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 Hachim Haddouti and Rob & Coronel, Ch6

  4. The Information System • 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 Hachim Haddouti and Rob & Coronel, Ch6

  5. The Information System (Con’t.) • 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 Hachim Haddouti and Rob & Coronel, Ch6

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

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

  8. 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) Hachim Haddouti and Rob & Coronel, Ch6

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

  10. 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 Hachim Haddouti and Rob & Coronel, Ch6

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

  12. 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 Hachim Haddouti and Rob & Coronel, Ch6

  13. 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) Hachim Haddouti and Rob & Coronel, Ch6

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

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

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

  17. 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 Hachim Haddouti and Rob & Coronel, Ch6

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

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

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

  21. 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 Hachim Haddouti and Rob & Coronel, Ch6

  22. 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 Hachim Haddouti and Rob & Coronel, Ch6

  23. 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 Hachim Haddouti and Rob & Coronel, Ch6

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

  25. 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 Hachim Haddouti and Rob & Coronel, Ch6

  26. 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 Hachim Haddouti and Rob & Coronel, Ch6

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

  28. 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 Hachim Haddouti and Rob & Coronel, Ch6

  29. 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 Hachim Haddouti and Rob & Coronel, Ch6

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

  31. 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 Hachim Haddouti and Rob & Coronel, Ch6

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

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