1.Describe what are Boolean Functions.
The ability to modify a scheme definition in one level without affecting a scheme definition in a higher level is called data independence.
There are two kinds:
Physical data independence
The ability to modify the physical scheme without causing application programs to be rewritten
Modifications at this level are usually to improve performance
Logical data independence
The ability to modify the conceptual scheme without causing application programs to be rewritten
Usually done when logical structure of database is altered
There are two kinds:
Physical data independence
The ability to modify the physical scheme without causing application programs to be rewritten
Modifications at this level are usually to improve performance
Logical data independence
The ability to modify the conceptual scheme without causing application programs to be rewritten
Usually done when logical structure of database is altered