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Exercise No. 36: Budget Rental Service (apa)

The following cube stores data about the Budget car rental service.

Cars are rent to customers who can be classified into customer groups (private, business, etc.). There's an option to rent a driver for the car as well. The car is serviced by a garage and belongs to a branch of the Budget car rental service. This branch belongs to the nationalwide operating Budget car rental service

We have five dimensions with the following hierarchical structure:

Table A.21.5.1 - the Budget car rental service

Please build the Aggregation Path Array and assume the following end-user requirements:

1) "a roll up by the time dimension starting at weeks for each customer group independent of the driver, the garage the car is serviced and the branch"

2) "a daily report for each combination of driver and branch, independent of the customer and the garage"

3) "a weekly report for each garage, irrespective of the customer, the driver and the branch"

Select the corresponding cells in the APA and choose the cubes to materialize, then highlight the derivatives of those cubes.

Solution

Figure A.E.21.1 - The resulting APA with the redundancy free-set highlighted

Size of the redundancy-free set (including the base cube): 108

Required cubes, the materialization decision and derivatives

The blue area represents the end-user requirement 1 ("a roll up by the time dimension starting at weeks for each customer group independent of the driver, the garage the car is serviced and the branch"), requirement 2 ("a daily report for each combination of driver and branch, independent of the customer and the garage") and requirement 3 ("a weekly report for each garage, irrespective of the customer, the driver and the branch").

Materializing cube v = (D_*,G_*,B_*,C_gr,T_w) (dark blue cell "T_w", representing end-user requirement 1), cube w = (D_dr,G_*,B_br,C_*,T_d) (dark green cell "C_*", representing end-user requirement 2) and cube x = (D_*,G_ga, B_*,C_*,T_w) (red cell "T_w", representing end-user requirement 3) offer us the following sets of derivatives.

Figure A.E.21.2 - Derivatives of cube v = (D_*,G_*,B_*,C_gr,T_w)

Figure A.E.21.3 - Derivatives of cube w = (D_dr,G_*,B_br,C_*,T_d)

Figure A.E.21.4 - Derivatives of cubex = (D_*,G_ga, B_*,C_*,T_w)

Figures A.E.21.2, A.E.21.3 and A.E.21.4 show that no end-user requirement is covered by the derivatives of another vector. To meet all end-user requirements we will have to materialize all three cubes, v, w and x.

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