Creating Custom Aggregates

Most aggregates are defined with a parent relation that identifies the parent-child relationships within the dimension. However, users may wish to create their own aggregates at runtime, perhaps for forecasting or what-if analysis, or just because they want to view the data in an unforeseen way. This is the process by which a custom aggregate is created:

1. Create a dimension value for the custom aggregate. The following command adds `bb' to the letter dimension:

   maintain letter add 'bb'
   
   

2. Create a MODEL object that contains an AGGREGATION function, which associates child dimension values with the new dimension value. The following model identifies bb as the parent of aab and aba. Note that the parent dimension value (in this case, bb) cannot already be defined as a parent in the parent relation (letter.letter).

   DEFINE LETTER.MODEL MODEL
   MODEL
   DIMENSION letter
   bb=AGGREGATION('aab' 'aba')
   
   

3. Execute an AGGMAP ADD command to append the model to an existing AGGMAP object.

   AGGMAP ADD letter.model TO letter.aggmap
   
   

   The aggregation map from Example 12-8 now looks like this:

   DEFINE LETTER.AGGMAP AGGMAP
   AGGMAP
   RELATION letter.letter PRECOMPUTE ('aa')
   END
   AGGMAP ADD letter.model
   
   

4. The model is executed only by the AGGREGATE function like the one shown here; the AGGREGATE command ignores it.

   REPORT AGGREGATE(units USING letter.aggmap)
   
   

5. If you wish to remove the model from the aggregation map during a session, use the AGGMAP REMOVE command.

   Important: The AGGMAP ADD command is automatically removed from an aggmap object at the end of a session.