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Exercise No. 39: Cassette (apa)

A customer asks a store assistant for a cassette via different modes of communication (phone, face to face, email, etc.). The cassette is released by a certain artist. The artist belongs to a certain music company. The time dimension consists of day, week and month.

We have five dimensions with the following hierarchical structure:

Table A.E.39.1 - cassette

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

1) "a complete drill-down by the time dimension down to week for each combination of mode of communication and assistant, irrespective of all other dimensions"

2) "a roll up by the time dimension starting at weeks for each assistant independent of all other dimensions"

3) "a monthly report for each combination of customer and artist 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.

Solution

Figure A.E.39.1 - The resulting APA with the redundancy free-set highlighted

Size of the redundancy-free set (including the base cube): 128

Required cubes, the materialization decision and derivatives

The blue area represents the end-user requirement 1 ("a complete drill-down by the time dimension down to week for each combination of mode of communication and assistant, irrespective of all other dimensions"), requirement 2 ("a roll up by the time dimension starting at weeks for each assistant independent of all other dimensions") and requirement 3 ("a monthly report for each combination of customer and artist independent of all other dimensions").

Materializing cube v = (CU_*,S_sa,M_mc,C_*,T_w) (dark blue cell "T_w", representing end-user requirement 1), cube w = (CU_*,S_sa,M_*,C_*,T_w) (dark green cell "T_w", representing end-user requirement 2) and cube x = (CU_cu,S_*,M_*,C_ar,T_m) (red cell "T_m", representing end-user requirement 3) offer us the following sets of derivatives.

Figure A.E.39.2 - Derivatives of cube v = (CU_*,S_sa,M_mc,C_*,T_w)

Figure A.E.39.3 - Derivatives of cube w = (CU_*,S_sa,M_*,C_*,T_w)

Figure A.E.39.4 - Derivatives of cube x = (CU_cu,S_*,M_*,C_ar,T_m)

Figures A.E.39.2 to A.E.39.4 show that end-user requirement 2 is covered by the derivatives of vector v. To meet all end-user requirements we will only have to materialize two cubes, v and x

Exercises List