Studierende stehen vor dem LC und blicken lächelnd einer Kollegin mit einer Mappe in der Hand nach.

Exercise No. 7: Car Sales (apa)

As the result of DFM Case "car sale" this cube stores data about a car sale.

We have three dimensions with the following hierarchical structure:

Table A.E.23.1 - car sale

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

1) "a weekly report on a car type, independent of the car dealer"

2) "a monthly report on a sales area, irrespective of the car"

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

Solution

Figure A.E.23.1 - The resulting APA with the redundancy free-set highlighted

Size of the redundancy-free set (including the base cube): 48

Required cubes, the materialization decision and derivatives

The blue area represents the end-user requirement 1 ( "a weekly report on a car type, independent of the car dealer") and requirement 2 ("a monthly report on a sales area, irrespective of the car").

Materializing cube v = (C_ty,CD_*,T_w) (dark blue cell "CD_*", representing end-user requirement 1) and cube w = (C_*, CD_sa, T_m) (dark green cell "T_m", representing end-user requirement 2) offer us the following sets of derivatives.

Figure A.E.23.2 - Derivatives of cube v = (C_ty,CD_*,T_w)

Figure A.E.23.3 - Derivatives of cube w = (C_*, CD_sa, T_m)

Figures A.E.23.2 and A.E.23.3 show that end-user requirement 2 is not covered by the derivatives of v. To meet all end-user requirements we will have to materialize both cubes, v and w.

This exercise is part of a case study: dfm - apa - log

Exercises List