2. The system of claim 1 , wherein evaluating the aggregation construct comprises evaluating the aggregation construct if and only if the existential term generates one or more tuples.
2. The system of claim 1 , wherein evaluating the aggregation construct comprises evaluating the aggregation construct if and only if the existential term generates one or more tuples. 3. The system of claim 2 , wherein the operations further comprise evaluating the existential term before the aggregation construct.