Optimal external memory planar point enclosureOptimal external memory planar point enclosure Πλήρης Δημοσίευση σε Συνέδριο Conference Full Paper 2015-10-172004enIn this paper we study the external memory planar point en- closure problem: Given N axis-parallel rectangles in the plane, construct a data structure on disk (an index) such that all K rectangles containing a query point can be reported I/O-efficiently. This problem has important applications in e.g. spatial and temporal databases, and is dual to the important and well-studied orthogonal range searching problem. Surpris- ingly, we show that one cannot construct a linear sized external memory point enclosure data structure that can be used to answer a query in O(logB N + K/B) I/Os, where B is the disk block size. To obtain this bound, Ω(N/B1−ε) disk blocks are needed for some constant ε > 0. With linear space, the best obtainable query bound is O(log2 N + K/B). To show this we prove a general lower bound on the tradeoff between the size of the data structure and its query cost. We also develop a family of structures with matching space and query bounds.http://creativecommons.org/licenses/by/4.0/12th Annual European Symposium (Algorithms - ESA 2004) Samoladas Vasilis Σαμολαδας Βασιλης Lars Arge Ke Yi