Describe logical data independence ?

Logical Data Independence - It is the capacity to modify the conceptual schema without having to change external schemas or application programs. The conceptual schema might be changed to expand the database (through adding a record type or data item), to change constraints, or to decrease the database (by removing a record type or data item). Only the view definition and the mappings required are changed in a DBMS that supports logical data independence. Changes to constraints could be applied to the conceptual schema without moving the external schemas or application programs.