Table A.E.29.1 - bus maintenance

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

1) "a roll up by the time dimension starting at quarters for each combination of bus and driver, independent of all other dimensions"

2) "a monthly report on the garage level independent of all other dimensions"

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

Figure A.E.29.1 - The resulting APA with the redundancy free-set highlighted

Size of the redundancy-free set (including the base cube): 72

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 quarters for each combination of bus and driver, independent of all other dimensions") and requirement 2 ("a monthly report on the garage level independent of all other dimensions").

Materializing cube v = (D_dr,M_*,B_bu,T_q) (dark blue cell "T_q", representing end-user requirement 1) and cube w = (D_*,M_ga,B_*,T_m) (dark green cell "B_*", representing end-user requirement 2) offer us the following sets of derivatives.

Figure A.E.29.2 - Derivatives of cube v = (D_dr,M_*,B_bu,T_q)

Figure A.E.29.3 - Derivatives of cube w = (D_*,M_ga,B_*,T_m)

Figures A.E.29.2 and A.E.29.3 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 both cubes, v and w.