Five Level Schema Architecture For FDBSs
The five level schema architecture includes the following:
- Local Schema is the conceptual concept expressed in primary data model of component DBMS.
- Component Schema is derived by translating local schema into a model called the canonical data model or common data model. They are useful when semantics missed in local schema are incorporated in the component. They help in integration of data for tightly coupled FDBS.
- Export Schema represents a subset of a component schema that is available to the FDBS. It may include access control information regarding its use by specific federation user. The export schema help in managing flow of control of data.
- Federated Schema is an integration of multiple export schema. It includes information on data distribution that is generated when integrating export schemas.
- External Schema defines a schema for a user/applications or a class of users/applications.
While accurately representing the state of the art in data integration, the Five Level Schema Architecture above does suffer from a major drawback, namely IT imposed look and feel. Modern data users demand control over how data is presented; their needs are somewhat in conflict with such bottom-up approaches to data integration.
Read more about this topic: Federated Database System
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