Aggregations contain these collections: Dimensions and their subordinate Levels collection, Measures, Datasources, and CustomProperties.
The Dimensions collection in an aggregation contains the definitions of the dimensions used by the aggregation.
The Measures collection in an aggregation contains the measures to be used in aggregation calculations.
The Datasources collection in an aggregation specifies the locations of data to be aggregated.
The CustomProperties collection contains Property objects that you can use to define additional properties for your own purposes.