Aggregate functions

SET function
The SET aggregation function takes a single-assign attribute and constructs a set of all of the (non-NULL) values from that attribute.

SET_INTERSECTIONS function
The SET_INTERSECTIONS aggregation function takes a multi-assign attribute and constructs a set that is the intersection of all of the values from that attribute.

SET_UNIONS function
The SET_UNIONS aggregation function takes a multi-assign attribute and constructs a set that is the union of all of the values from that attribute.