Three-schema Architecture in Database Systems

Three-schema Architecture in Database Systems

The three-schema architecture is a framework used in database systems to separate the different levels of abstraction in data representation and management. It consists of three levels: the internal level, the conceptual level, and the external level.

Internal Level

• Describes how data is physically stored on storage devices (e.g., file structures, indexes, access paths)
• Deals with data compression, encryption, and optimization for performance
• Closest to the hardware layer and handles low-level data management operations

Conceptual Level

• Represents the logical structure of the entire database, including entities, relationships, and constraints
• Provides a unified view of all data in the organization, independent of physical storage details
• Serves as a bridge between the internal and external levels, ensuring data independence

External Level

• Defines user-specific views of the database tailored to different application requirements
• Multiple external schemas can exist for different user groups or applications
• Provides data abstraction and security by limiting access to only relevant portions of the database