An intersect relation between a subset and a number of super sets defines the subset as the intersection of all its supersets, i.e. the superset can be considered as derived from its subsets. Adding an instance to the superset will add this instance to all subsets.
Intersect relations for controlled extents are maintained automatically, which means, that one cannot remove instances from an intersect extent. Instances have to be removed from appropriate base extents, instead.