实用数据库设计方法学

1 .Chapter 10 Practical Database Design Methodology and Use of UML Diagrams

2 .Chapter 10 Outline The Role of Information Systems in Organizations The Database Design and Implementation Process Automated Database Design Tools

3 .Practical Database Design Methodology and Use of UML Diagrams Design methodology Target database managed by some type of database management system Various design methodologies Large database Several dozen gigabytes of data and a schema with more than 30 or 40 distinct entity types

4 .The Role of Information Systems in Organizations Organizational context for using database systems Organizations have created the position of database administrator (DBA) and database administration departments Information technology (IT) and information resource management (IRM) departments Key to successful business management

5 .The Role of Information Systems in Organizations Database systems are integral components in computer-based information systems Personal computers and database system-like software products Utilized by users who previously belonged to the category of casual and occasional database users Personal databases gaining popularity Databases are distributed over multiple computer systems Better local control and faster local processing

6 .Slide 12- 6 Organizational Context for using Database Systems Consolidation of data across organization Maintenance of complex data Simplicity of developing new applications Data independence Protecting application programs from changes in the underlying logical organization and in the physical access paths and storage structures External Schemas Allow the same data to be used for multiple apps with each application having its own view of the data

7 .The Role of Information Systems in Organizations Data dictionary systems or information repositories Mini DBMSs Manage meta-data High-performance transaction processing systems require around-the-clock nonstop operation Performance is critical

8 .The Information System Life Cycle Information system (IS) Resources involved in collection, management, use, and dissemination of information resources of organization

9 .The Information System Life Cycle Macro life cycle Feasibility analysis Requirements collection and analysis Design Implementation Validation and acceptance testing Requirements collection and analysis

10 .Slide 12- 10 Phases of Information System Life Cycle Feasibility Analysis Analyzing potential application areas Identifying the economics of information gathering and dissemination Performing cost benefit studies Setting up priorities among applications Requirement Collection and Analysis Detailed Requirements Collection Interaction with Users Design Design of Database System Design of programs that use and process the database

11 .Slide 12- 11 Phases of Information System Life Cycle Implementation Information system is implemented Database is loaded & its transactions are implemented and tested Validation and Acceptance Testing Testing against user’s requirements Testing against performance criteria Deployment, Operation and Maintenance Data conversion Training System maintenance Performance monitoring Database tuning

12 .The Information System Life Cycle The database application system life cycle: micro life cycle System definition Database design Database implementation Loading or data conversion

13 .The Information System Life Cycle Application conversion Testing and validation Operation Monitoring and maintenance

14 .Slide 12- 14 Database System Life Cycle System definition Defining scope of database system, its users and applications Database Design Logical and physical design of the database system on the chosen DBMS Database implementation Specifying conceptual, external and internal database definitions Creating empty database files Implementing software applications

15 .Slide 12- 15 Database System Life Cycle Loading or data conversion Populating the database Application conversion Converting applications to the new system Testing and validation Operation Running the new system Monitoring and maintenance System maintenance Performance monitoring

16 .The Database Design and Implementation Process Design logical and physical structure of one or more databases Accommodate the information needs of the users in an organization for a defined set of applications Goals of database design Very hard to accomplish and measure Often begins with informal and incomplete requirements

17 .The Database Design and Implementation Process Main phases of the overall database design and implementation process: 1. Requirements collection and analysis 2. Conceptual database design 3. Choice of a DBMS 4. Data model mapping (also called logical database design) 5. Physical database design 6. Database system implementation and tuning

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19 .The Database Design and Implementation Process Parallel activities Data content , structure , and constraints of the database Design of database applications Data-driven versus process-driven design Feedback loops among phases and within phases are common

20 .The Database Design and Implementation Process Heart of the database design process Conceptual database design (Phase 2) Data model mapping (Phase 4) Physical database design (Phase 5) Database system implementation and tuning (Phase 6)

21 .Phase 1: Requirements Collection and Analysis Activities Identify application areas and user groups Study and analyze documentation Study current operating environment Collect written responses from users

22 .Phase 1 Requirements specification techniques Oriented analysis (OOA) Data flow diagrams (DFDs Refinement of application goals Computer-aided

23 .Phase 2: Conceptual Database Design Phase 2a: Conceptual Schema Design Important to use a conceptual high-level data model Approaches to conceptual schema design Centralized (or one shot) schema design approach View integration approach

24 .Phase 2: Strategies for schema design Top-down strategy Bottom-up strategy Inside-out strategy Mixed strategy Schema (view) integration Identify correspondences/conflicts among schemas: Naming conflicts, type conflicts, domain (value set) conflicts, conflicts among constraints Modify views to conform to one another Merge of views and restructure

25 .Slide 12- 25 Strategies for Schema Design Top Down Strategy Start with a schema containing high-level abstractions and then apply successive top-down refinements

26 .Slide 12- 26 Strategies for Schema Design Bottom-Up Strategy Start with a schema containing basics abstractions and then combine or add to these abstractions

27 .Slide 12- 27 Strategies for Schema Design Inside-out Strategy Start with central set of concepts and then spread outward by considering new concepts in the vicinity of existing ones Mixed Strategy Use a combination of top-down and bottom-up strategies

28 .Phase 2: Strategies for the view integration process Binary ladder integration N-ary integration Binary balanced strategy Mixed strategy Phase 2b: Transaction Design In parallel with Phase 2a Specify transactions at a conceptual level Identify i nput/output and functional behavior Notation for specifying processes

29 .Slide 12- 29 View Integration Strategies Binary Ladder Integration Two similar schemas are integrated first and the resulting schema is then integrated with another schema The process is repeated until all schemas are integrated N-ary Integration All views are integrated in one procedure after analysis and specification of their correspondences Requires computerized tools for large designs