The practice of guiding a search engine based on query logs observed from the engine's user population provides large volumes of data but potentially also sacrifices the privacy of the user. In this paper, we ask the following question: Is it possible, given rich instrumented data from a panel and usability study data, to observe complete information without routinely analyzing query logs? What...

Reverse nearest neighbor queries are defined as follows: Given an input point-set P , and a query point q, find all the points p in P whose nearest point in P ∪ {q} \ {p} is q. We give a data structure to answer reverse nearest neighbor queries in fixed-dimensional Euclidean space. Our data structure uses O(n) space, its preprocessing time is O(n log n), and its query time is O(log n).

Computing the visibility polygon, VP, of a point in a polygonal scene, is a classical problem that has been studied extensively. In this paper, we consider the problem of computing VP for any query point efficiently, with some additional preprocessing phase. The scene consists of a set of obstacles, of total complexity O(n). We show for a query point q, V P (q) can be computed in logarithmic ti...

We revisit classical geometric search problems under the assumption of rational coordinates. Our main result is a tight bound for point separation, ie, to determine whether n given points lie on one side of a query line. We show that with polynomial storage the query time is Θ(log b/ log log b), where b is the bit length of the rationals used in specifying the line and the points. The lower bou...

Given a set of n objects each characterized by d attributes speci ed at m xed time instances we are interested in the problem of designing space e cient indexing structures such that arbitrary temporal range search queries can be handled e ciently When m our problem reduces to the d dimensional orthogonal search problem We establish e cient data structures to handle several classes of the gener...

We present OWL-log, which is an implementation of the ALlog hybrid knowledge representation system where the Description Logics component is extended to the Web Ontology Language OWL DL. We implemented an OWL-log reasoner coupled to the OWL reasoner Pellet and explored different query-answering strategies. We conducted an experimental study using a modified version of the LUBM benchmark in orde...

Let S be a set of points in R. Given a geometric spanner graph, G = (S, E), with constant dilation t, and a positive constant ε, we show how to construct a (1 + ε)-spanner of G with O(|S|) edges in time O(|E|+ |S| log |S|). Previous algorithms require a preliminary step in which the edges are sorted in non-decreasing order of their lengths and, thus, have running time Ω(|E| log |S|). We obtain ...

We prove that to store n bits x ∈ {0, 1}n so that each prefix sum (a.k.a. rank) query Sum(i) := ∑ k≤i xk can be answered by non-adaptively probing q cells of lg n bits, one needs memory n + n/ log n. This matches a recent upper bound of n+ n/ log n by Pǎtraşcu (FOCS 2008), also non-adaptive. We also obtain a n + n/ log O(q) n lower bound for storing a string of balanced brackets so that each Ma...

Binary search finds a given element in a sorted array with an optimal number of log n queries. However, binary search fails even when the array is only slightly disordered or access to its elements is subject to errors. We study the worst-case query complexity of search algorithms that are robust to imprecise queries and that adapt to perturbations of the order of the elements. We give (almost)...

The polygon retrieval problem on points is the problem of preprocessing a set of n points on the plane, so that given a polygon query, the subset of points lying inside it can be reported efficiently. It is of great interest in areas such as Computer Graphics, CAD applications, Spatial Databases and GIS developing tasks. In this paper we study the problem of canonical k-vertex polygon queries o...