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

Exercise No. 51: Mails via a Webmail Tool (apa)

This cube stores data about getting mails via a webmail tool.

A user who is of a certain type gets a mail. The mail is delivered by an Internet Service Provider (ISP) and may be encrypted by a certain encryption standard. The mail itself is of a certain type (plain text, html style, etc.). The mail type itself belongs to a certain group. The time dimension consists of month and quarter.

We have five dimensions with the following hierarchical structure:

Table A.E.43.1 - getting mails

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 combination of isp and encryption standard, independent of all other dimensions"

2) "a monthly report on the mail type 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.

Solution

Figure A.E.43.1 - The resulting APA with the redundancy free-set highlighted

Size of the redundancy-free set (including the base cube): 192

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 combination of isp and encryption standard, independent of all other dimensions") and requirement 2 ("a monthly report on the mail type level independent of all other dimensions").

Materializing cube v = (I_is,E_es,U_*,M_*,T_w) (dark blue cell "T_w", representing end-user requirement 1) and cube w = (I_*,E_*,U_*,M_ty,T_m) (dark green cell "T_m", representing end-user requirement 2) offer us the following sets of derivatives.

Figure A.E.43.2 - Derivatives of cube v = (I_is,E_es,U_*,M_*,T_w)

Figure A.E.43.3 - Derivatives of cube w = (I_*,E_*,U_*,M_ty,T_m)

Figures A.E.43.2 and A.E.43.3 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.