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Chapter 8 Creating Explicit Dimension Sets

If you do not create an explicit dimension set to calculate these data cubes, the analytic calculation engine

calculates the sales for all products in all regions during all months, even if some of these combinations are

not valid. In other words, the analytic calculation engine calculates the sales for french fries f or all months

in Asia, even though the company does not sell french fries in Asia. Additionally, the analytic calculation

engine calculates the s ales for french fries during all months in Africa, even though the company only sells

french fries in Africa during the summer.

In total, wit

hout using an explicit dimension set, the analytic calculation engine performs 48 calculations for

the SALES dat

acube:

(2 PRODUCTS *

2 REGIONS * 12 MONTHS)

The analytic calculation engine generates the val ue of 0 for each invalid member combination, taking valuable

time to do so. These invalid member values are:

• Not saved to the main record.

• Not displayed to end users in the application.

End users view invalid member combinations as blank cells.

To prevent th

is unneeded calculation of data, you should create an explicit dimension set consisting of the

PRODUCTS, RE

GIONS, and MONTHS dimensions. The analytic calculation engine uses this explicit

dimension se

t, plus the UNIT_SALES and UNIT_PRICE input data cubes, to determine the explicit tuples.

Using these

tuples, the analytic calculation engine only calculates the necessary values.

Note. The analytic calculation engine uses the input cubes that comprise the relevant data cube’s formula

to instantiate the explicit tuples that it uses to calculate the data cube.

In total, the analytic calculation engine performs 27 calculations for the SALES data cube:

(1 PRODUCT * 2 REGIONS * 12 MONTHS) + (1 PRODUCT * 1 REGIONS * 3 MONTHS)

Example 2: Explicit Dimension Supersets and Subsets

An analytic m

odel contains the SALES data cube. These dimensions are attached to this data cube:

• PRODUCTS

•REGIONS

•ORDER_ID

• BUSINESS_UNIT

• DEPT_ID

• EMPL_ID

You h ave defined these explicit dimension sets:

• SET_1: PRODU

CTS, REGIONS, ORDER_ID (Priority 1).

• SET_2: PRODU

CTS, REGIONS (Priority 2).

• SET_3: REGIO

NS, ORDER_ID (Priority 3).

• SET_4: DEPT_

ID, EMPL_ID (Priority 4).

The explicit dimension subset (PRODUCTS, REGIONS) exists at a lower priority than its superset

(PRODUCTS, REGIONS, ORDER_ID). The subset is in row 2; the superset is in row 1. The analytic

calculation engine takes the cross product of the following to instantiate the valid combinations of dimension

members for the SALES data cube: