It's possible to define regions that overlap. In other words, one region can be defined for /a/b/c , and another defined for /a/b/c/d (which is just the d subtree of the /a/b/c sub-tree). The algorithm, in order to handle scenarios like this consistently, will always choose the first region it encounters. In this way, if the algorithm needed to decide how to handle /a/b/c/d/e , it would start from there and work its way up the tree until it hits the first defined region - in this case /a/b/c/d .