Suppose that a data warehouse consists of the three dimensions time, doctor, and patient, and the two measures count and charge, where charge is the fee that a doctor charges a patient for a visit.

a. Enumerate three classes of schemas that are popularly used for modeling data warehouses.

b. Draw a schema diagram for the above data warehouse using one of the schema classes listed in (a).

c. Starting with the base cuboid [day,doctor, patient], what specific OLAP operations should be performed in order to list the total fee collected by each doctor in 2010 ?

d. To obtain the same list, write an SQL query assuming the data is stored in a relational database with the schema fee (day, month, year, doctor, hospital, patient, count, charge).