The three-schema architecture is a convenient tool for the user to visualize the schema levels in a database system.
Three Schema Architecture
The External Schema
• Defines one view of the data as seen by a specific set of applications or end users,
The conceptual schema
• Defines data from perspective systems designer,
• Independent of end users & data storage mechanism
The Internal Schema
• Defines how data is organized, stored and manipulated inside the application itself
• Totally dependent on particular implementation
The three-schema architecture explains the concept of data independence, which is defined as the capacity to the change the schema at one level of the database system without having to change the schema at next higher level. The three-schema architecture makes it easier to achieve true data independence.
Three Schema Architecture
The External Schema
• Defines one view of the data as seen by a specific set of applications or end users,
The conceptual schema
• Defines data from perspective systems designer,
• Independent of end users & data storage mechanism
The Internal Schema
• Defines how data is organized, stored and manipulated inside the application itself
• Totally dependent on particular implementation
The three-schema architecture explains the concept of data independence, which is defined as the capacity to the change the schema at one level of the database system without having to change the schema at next higher level. The three-schema architecture makes it easier to achieve true data independence.
