a$.$ Give a diagram that clearly articulates the three levels of data abstraction in a database, one of them being the view level $(4$ marks$).$ Hint: be sure to not just have one encompassing box for the view level.

b$.$ Define logical semi$-$data independence $(1$ mark$)$

c$.$ Give the motivation behind logical semi$-$data independence $-$ why is it needed at the application layer and why is it desirable? $(1$ mark$)$

d$.$ Describe how logical semi$-$data independence can be achieved $(1$ mark$).$ Hint: do not confuse the application layer with the views.

e$.$ Define physical data independence $(1$ mark$)$

f$.$ Give the motivation behind physical data independence mark