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The ANSI/SPARC Architecture of a Database Environment

The ANSI/SPARC Architecture of a Database Environment Lecture 2 Schema and instance database schema the description of the database is called the database schema or intension; specified at the creation of the database not expected to change very often database instance

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The ANSI/SPARC Architecture of a Database Environment

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  1. The ANSI/SPARC Architectureof a Database Environment Lecture 2

  2. Schema and instance • database schema • the description of the database is called the database schema or intension; • specified at the creation of the database • not expected to change very often • database instance • the raw data that populates a database at a particular moment in time is called a database instance of the extension of the database

  3. Schema and instance - example

  4. Levels of access to data

  5. The three ANSI/SPARC levels of abstraction

  6. Schemas and mappings • schemas • external • conceptual • internal • mappings • external / conceptual • conceptual / internal • data catalogue/dictionary  schemas  mappings

  7. External / conceptual example

  8. Conceptual / internal - example

  9. Program - data independence • physical • the immunity of application programs to changes at the internal level • logical • the immunity of application programs to changes at the conceptual level

  10. The components of a database environment

  11. Data • types • primary • derived • characteristics • integrated • shared • extensive • data = raw data + data dictionary

  12. Hardware • storage space • permanent / secondary • temporary / primary • computational power

  13. Software

  14. Application programs • user developed • in a third generation language • provide an embedded data sub-language • provided by developers • fourth generation language • examples: query processors, statistical packages, reports/forms generators

  15. Database management system • provides support for • data manipulation / definition • data sub-languages (computationally incomplete) • data integrity • security control • recovery services • concurrency facilities • data communication • accessing the data dictionary • why needed? applications’ automatic access to the DB

  16. People • data administrator • relevance and meaning of data; standards; policy • database administrator • design, implementation and maintenance of the DB • application programmers • end user

  17. Summary • the three level ANSI/SPARC architecture of a database environment • the components of a database environment

  18. Activity A2 Which role within a database environment would you prefer to be in, if you were able to choose? Why? Which activities would you be interested in performing? How would you like to co-operate with the people performing the other roles?

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