Data Independence

  

Data Independence is the type of data transparency that matters for DBMS. It refers to the security of user application to the user changes made in the organization of the data. 

It is the capacity to modify a scheme definition at one level without affecting a scheme definition at a higher level.

There are two kinds of data independence:

1. Physical data independence: It is the capacity to modify the physical scheme without having alteration to the conceptual schema.
For example, the addition or removal of new entities, attributes, or relationships to the conceptual schema should be possible without having to change existing external schemas or having to rewrite existing application programs.

For example, a change to the internal schema, such as using different file organization or storage structures, storage devices, or indexing strategy, should be possible without having to change the conceptual or external schemas.

2. Logical data independence: It is the capacity to modify the logical or conceptual scheme(user view) without having an alteration in the external schema.