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Exercise No. 10: Cost Center (apa)

The following cube stores data about a cost center.

Building projects which are located in a certain country belong to a cost center. A certain cost accounting staff - who belongs to the cost accounting department - is responsible for each cost center. Each cost center has serveral employees assigned.

We have four dimensions with the following hierarchical structure:

Table A.E.4.1 - cost center

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

1) "a monthly report for each building project independent of the employee and the cost accounting staff"

2) "an annual report for each type of employee, irrespective of the building project and the cost accounting staff"

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

Solution

Figure A.E.4.1 - The resulting APA with the redundancy free-set highlighted

Size of the redundancy-free set (including the base cube): 56

Required cubes, the materialization decision and derivatives

The blue area represents the end-user requirement 1 ("a monthly report for each building project independent of the employee and the cost accounting staff") and requirement 2 ("an annual report for each type of employee, irrespective of the building project and the cost accounting staff").

Materializing cube v = (B_pr, E_*,C_*,T_m) (dark blue cell "C_*", representing end-user requirement 1) and cube w = (B_*,E_ty, C_*, T_y) (dark green cell "T_y", representing end-user requirement 2) offer us the following sets of derivatives.

Figure A.E.4.2 - Derivatives of cube v = (B_pr, E_*,C_*,T_m)

Figure A.E.4.3 - Derivatives of cube w = (B_*,E_ty, C_*, T_y)

Figures A.E.4.2 and A.E.4.3 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