I think I'll go for the Algorithm:: namespace, b/c I'm not really sure what structure it is, though it seems closer to a Segment tree from wikipedia'ing.

(What I do is, given a list of intervals, I sort them by midpoint, and join adjacent intervals into parent nodes with interval (min(children's starts), max(children's ends)). The idea being that every node encompasses it's descendants, so that you can query by traversing nodes overlapping the query interval.)