Data Independence

Data Independence is a clear separation of data from programs, that means change occurring in schema at one level of the database without having to change the schema at the next higher level. Database provides two types of data independence, viz.

• Physical Data Independence.
• Logical Data Independence.

Physical Data Independence is the change occurring in internal schemas without having to change the conceptual schemas. Conceptual schemas may be changed for database expansion.

Logical Data Independence is the change occurring in conceptual schemas without having to change the external schemas. Thus the external schemas also need not to be changed.

Here the physical, conceptual and external schemas are the three levels of the Three Schema Architecture.