Chapter 4. Modeling dynamic cubes 77
4.3.5 Parent-child dimensions
Parent-child dimensions do not have defined levels. The data of the parent and child
attributes determine how the members are generated and assembled in to a member tree.
They can have only one hierarchy.
Functions that reference a member in the context of a level or descendants return each child
member that is that many member nodes down the tree. If you have an unbalanced hierarchy,
the member tree will generate without any additional modeling required.
If the parent-child dimension is a slowly changing dimension, the parent and child attributes
need to be surrogate keys.
Data members are members that contain values that are associated with the parent member
itself. The data member allows you to see those values. If the data member does not get
specified, the values will still be aggregated into the parent member but there will be no
indication of the source of that value. For aggregations such as
sum, it would be fairly readily
apparent that the parent member had values that are associated with it. For others, such as
average, it is would be less so. A good idea is to include them by setting the show data
member property value to true and setting the caption of data members property value to be
Parent’s caption.
Root member will contain the ultimate parent, enabling you to model so that the ultimate
parent member is displayed in the member tree. If you do not set a value for the root member
property on the root member of the dimension for the member tree will be the ultimate parent.
The caption for the member as displayed in the member tree in the Cognos studios will be the
dimension’s name. The actual member name will be used in reports.
Figure 4-11 shows a parent-child dimension where the show data member property was set
to true and the caption of data members value was set to the parent’s caption.
Figure 4-11 Parent-child dimension
An example of a parent-child dimension is in 4.6, “Slowly changing dimensions” on page 79.
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