Question

Discuss the concept of data independence with respect to the three schema architecture.

Answer 1

ANSWER -

DATA INDEPENDENCE -

It is the capacity to change the schema of one level of three schema architecture in DBMS without having to change the next higher level of the schema. This can be explained with three schema architecture.

THREE SCHEMA ARCHITECTURE -

In DBMS, the main goal of three schema architecture is to separate the user level/external level from the physical database. There 3 levels , namely -

1. Internal level - It includes internal schema, which describes the physical storage of database.
2. Conceptual level - Includes conceptual schema, which hides the details of physical storage and data is represented in form of database tables.
3. External level - Includes external view, which specifies the data which particular user group are interested in and hiding the rest of database from the user.

The concept of data independence with respect to the three schema architecture , it is classified into two -

• Logical Data Independence - It is ability to change or modify the conceptual schema of the conceptual level without having to change the external schema. It is difficult to achieve compared to the physical data independence because the changes made in conceptual level affects the view in external level.
• Physical Data Independence - It is the ability to change or modify the internal schema of the internal level without having to change the conceptual schema, hence not affecting the external schema. It is easier to achieve and is used and implemented in most of the database management system.

This is the concept of data independency with respect to three-schema architecture.

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