Data independence

Data independence is the type of data transparency that matters for a centralized DBMS. It refers to the immunity of user applications to changes in the definition and organization of data, and vice-versa.

Physical data independence deals with hiding the details of the storage structure from user applications. The application should not be involved with these issues, since there is no difference in the operation carried out against the data.

There are two levels of data independence.

First level

The logical structure of the data and is known as the schema definition. In general, if a user application operates on a subset of the attributes of a relation, it should not be affected later when new attributes are added to the same relation.

Second level

The physical structure of the data and it is referred to as physical data description.