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Data Dictionary Storage

  1. The database also needs to store information about the relations, known as the data dictionary. This includes: plus data on the system users: plus (possibly) statistical and descriptive data:
  2. When we look at indices (Chapter 11), we'll also see a need to store information about each index on each relation:
  3. This information is, in itself, a miniature database. We can use the database to store data about itself, simplifying the overall structure of the system, and allowing the full power of the database to be used to permit fast access to system data.
  4. The exact choice of how to represent system data using relations must be made by the system designer. One possible representation follows.

     aaaaaaaaaaaa¯System-catalog-schema = (relation-name, number-attrs)

    Attr-schema = (attr-name, rel-name, domain-type, position, length)

    User-schema = (user-name, encrypted-password, group)

    Index-schema = (index-name, rel-name, index-type, index-attr)

    View-schema = (view-name, definition)

Osmar Zaiane
Tue Jul 7 16:00:21 PDT 1998