Monday, 28 November 2011

Advantages and Types of Database System

  • reduction in data redundancy
    • shared rather than independent databases
      • reduces problem of inconsistencies in stored information, e.g. different addresses in different departments for the same customer
  • maintenance of data integrity and quality
  • data are self-documented or self-descriptive
    • information on the meaning or interpretation of the data can be stored in the database, e.g. names of items, metadata
  • avoidance of inconsistencies
    • data must follow prescribed models, rules, standards
  • reduced cost of software development
    • many fundamental operations taken care of, however DBMS software can be expensive to install and maintain
  • security restrictions
    • database includes security tools to control access, particularly for writing
  • several models for databases:
    • tabular ("flat file") - data in a single table
    • hierarchical
    • network
    • relational
  • the hierarchical, network and relational models all try to deal with the same problem with tabular data:
    • inability to deal with more than one type of object, or with relationships between objects
    • e.g. database may need to handle information on aircraft, crew, flights and passengers - four types of records with different attributes, but with relationships between them (e.g. "is booked on" between passenger and flight)
  • database systems originated in the late 1950s and early 1960s largely by research and development of IBM Corporation
  • most developments were responses to needs of business, military, government and educational institutions - complex organizations with complex data and information needs
  • trend through time has been increasing separation between the user and the physical representation of the data - increasing "transparency"

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