SBVR — What is an aggregation formulation?

Doc: dtc/06-03-02
Date: March 2006
Version: Interim Convenience Document
Chapter: 9.1.1.9
Pages:
Nature: Editorial
Severity: minor

Description:

Recommendation:

In 9.1.1.9, the definition of 'aggregation formulation' is difficult to interpret. It seems to say it is an assertion of equality between two sets (or multisets), one of which is the value of a variable (bindable target?) and the other is the result of the projection. If that is what is intended, at least a Note should say this.

And in the Example about averages of ages, it is difficult to tell exactly what is supposed to be the 'aggregation formulation'. The model is:
AVERAGE( project car.age from car such that car is-owned-by b such that b is local-branch )
that is, a function of a projection that is based on a selection that is based on a selection. Which of these four operations is the aggregation formulation? But the logical formulation that is the rule has the form:
number is-less-than number
where the first number is the result of the 'average' function (which has no SBVR model I can find).

Provide a better definition of 'aggregation formulation'. Remove the note. Improve the example and give its full formulation.