Aggregation
BIRT 2.5 now has a really nice Aggregation visual component.
In the previous versions of BIRT, aggregations were expressions that one would put into the Expression Builder using the Data component. This has changed in newer versions of BIRT to use a simple graphical component that gets displayed visually, and adds in a list of aggregations that are available to the user. This subject will be covered in detail in Chapter 5,