Instances and Schemes
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- Databases change over time.
- The information in a database at a particular point in time is
called an instance of the database.
- The overall design of the database is called the database scheme.
- Analogy with programming languages:
- Data type definition - scheme
- Value of a variable - instance
- There are several schemes, corresponding to levels of abstraction:
- Physical scheme
- Conceptual scheme
- Subscheme (can be many)
Page created and maintained by Osmar R. Zaï ane
Sun Sep 10 16:58:49 PDT 1995