[Database] 2주 2차, 3주 1차 : Database Approach

- Database Approach

• Traditional file processing : Each user defines and implements the files needed for a specific software application
• Database approach : Single repository maintains data that defined once and then accessed by various users
• Main characteristics of database approach
  • Self-describing nature of a database system
    • Database system contains complete definition of structure and constraints
    • Meta-data : Describes structure of the database
    • Database catalog used by
    • DBMS software
    • Database users who need information about database structure
  • Insulation between programs and data
    • Program-data independence
    • Program-operation independence
  • Data abstraction
    • It allows program-data independence and program-operation independence
    • Conceptual representation of data
    • Data model
  • Support of multiple views of the data
    • View
      • Subset of the database
      • Contains virtual data derived from the database files but is not explicitly stored
    • Multiuser DBMS
      • Users have a variety of distinct applications
      • Must provide facilities for defining multiple views
• Actor on the scene
  • Database administers (DBA) are responsible for
    • Authorizing access to the database
    • Coordinating and monitoring its use
    • Acquiring software and hardware resources
  • Database designers are responsible for
    • Identifying the data to be stored
    • Choosing appropriate structures to represent and store this data
  • End users
    • People whose jobs require access to the database
    • Types
      • Casual end users (때때로 DB 접근)
      • Naïve or parametric end users
      • Sophisticated end users (Scientists)
      • Standalone users (Maintain personal databases)
    • System analysts
    • Application programmer
• Worker behind the scene
  • DBMS system designer and implementers
  • Tool developers
  • Operators and maintenance personnel
• Advantages of using the DBMS approach
  • Controlling redundancy
    • Data normalization
    • Denormalization
  • Restricting unauthorized access
    • Security and authorization subsystem
    • Privileged software (특정 사람만 이용 가능한 SW)
  • Providing persistent storage for program object
    • Impedance mismatch problem : Object-oriented database typically offer data structure compatibility
  • Providing storage structures and search techniques for efficient query processing
    • Indexes
      • Text data : B+ tree
      • Multi-media data : R+ tree
    • Buffering and caching
    • Query processing and optimization
  • Providing backup and recovery
    • Backup and recovery subsystem of the DBMS is responsible for recovery
  • Providing multiple user interfaces
    • Graphical user interfaces (GUIs)
  • Representing complex relationships among data
  • Enforcing integrity constraints
    • Referential integrity constraint
    • Key or uniqueness constraint
    • Business rules
    • Inherent rules of data model
  • Permitting inferencing and actions using rules
    • Deductive database systems
    • Trigger
    • Stored procedures
  • Additional implications of using the database approach
    • Reduced application development time
    • Flexibility
    • Availability of up-to-date information
    • Economies of scale (Data와 Application을 통합하여 Cost를 줄임)