Data Independence:
                                         The ability to modify the conceptual schema without having changes the external schema or application program, or to modify the internal schema without having changes the conceptual schema .

 Data Independence may be categorised by-----
          1. Logical data independence:
                                                                   The ability to modify(change) the conceptual schema without having changes external schema or application program we may be changed the conceptual schema to explain the database( by adding a new record type or data item), or to reduce the database (by removing a record type or data item).
          
           2. Physical data independence:
                                                                    The ability to modify(change) the physical schema without having changes the conceptual schema. Change to the internal schema may be needed because some physical file add to be recognised.