[rules-users] exists + normal column constraints - how many times a rule is cal led in the end????

Hi, I'm not sure my understanding of 'existential quantifiers' is correct. Hopefully, someone can clear it up a bit... Providing I have the following fact class: Person(role: parent/child, name) And following facts: 1: parent, John 2: parent, Alice 3: parent, Steve 4: parent, Jane 5: child, Eric 6: child, Rob 7: child, May 8: child, April I expect the rule Rule "iterate children if at least one parent is found" When exists Person(role == 'parent') $child: Person(role == 'child') Then // do smth for each $child if at least one parent is found End To iterate through all 'child' persons (facts 5 through 8), ie the action will be called exactly 4 times. Is this correct? What would happen if I swap the order of the conditions (with 'parent exists' constrain going _after_ 'child' constraint): When $child: Person(role == 'child') exists Person(role == 'parent') Thanks, Vlad