Logical Data Warehouse Design - Data Warehouse Systems: Design and Implementation - page 165

Role-playing dimensions are defined in Mondrian using the concept of shared
dimensions as we show below, where the shared dimension is Time :

< Cube name= ' Sales ' > 1

< Dimensions > 2

< Dimension name= ' Order Date ' source= ' Time ' / >

3

< Dimension name= ' Due Date ' source= ' Time ' / > 4

< Dimension name= ' Shipped Date ' source= ' Time ' / > 5

< Dimension name= ' Employee ' table= ' Employee ' key= ' Employee Key ' >

6

...

7

< /Dimension >

8

< /Dimensions >

9

...

10

< /Cube >

11

As we have seen, snowflake dimensions involve more than one table.
For example, the Product dimension involves tables Product and Category .
When defining dimensions based on snowflake schemas in Mondrian, it is
necessary to define in which table we can find the dimension attributes, as
shown next:

< Dimension name= ' Product ' table= ' Product ' key= ' Product Key ' >

1

< Attributes >

2

< Attribute name= ' Category Name ' keyColumn= ' CategoryName '

3

table= ' Category ' / >

4

5 ...
6 < Attribute name= ' Product Name ' keyColumn= ' ProductName ' / >
7 ...
8 < /Attributes >
9 < Hierarchies >
10 < Hierarchy name= ' Categories ' hasAll= ' true ' >
11 < Level name= ' Category ' attribute= ' Category Name ' / >
12 < Level name= ' Product ' attribute= ' Product Name ' / >
13 < /Hierarchy >
14 < /Hierarchies >
15 < /Dimension >

As can be seen above, the definition of attribute Category Name states that it
comes from table Category (lines 3-4). On the other hand, when defining the
attribute Product Name the table is not specified, by default it will be found
in the table defined in the Dimension element, that is, the Product table.
We show next how a parent-child (or recursive ) hierarchy can
be defined in Mondrian using the Supervision hierarchy in the Employee
dimension:

< Dimension name= ' Employee ' table= ' Employee ' key= ' Employee Key ' > 1

< Attributes > 2

< Attribute name= ' Employee Key ' keyColumn= ' EmployeeKey ' / >

3

...

4

< Attribute name= ' Supervisor Key ' keyColumn= ' SupervisorKey ' / >

5

< /Attributes >

6