The B-tree is a fundamental secondary index structure that is widely used for answering one-dimensional range reporting queries. Given a set of N keys, a range query can be answered in O(log B N M + K B ) I/Os, where B is the disk block size, K the output size, and M the size of the main memory buffer. When keys are inserted or deleted, the Btree is updated in O(log B N) I/Os, if we require the...

Many search engines and other web applications suggest auto-completions as the user types in a query. The suggestions are generated from hidden underlying databases, such as query logs, directories, and lexicons. These databases consist of interesting and useful information, but they are typically not directly accessible. In this paper we describe two algorithms for sampling suggestions using o...

Passage retrieval is usually defined as the task of searching for passages which may contain the answer for a given query. While these approaches are very e cient when dealing with texts, applied to log files (i.e. semi-structured data containing both numerical and symbolic information) they usually provide irrelevant or useless results. Nevertheless one appealing way for improving the results ...

We consider the two-dimensional Range Minimum Query problem: for a static (m × n)-matrix of size N = mn which may be preprocessed, answer on-line queries of the form “where is the position of a minimum element in an axis-parallel rectangle?”. Unlike the onedimensional version of this problem which can be solved in provably optimal time and space, the higher-dimensional case has received much le...

In this paper, we consider some shortest path related problems on interval and circular-arc graphs. For the all-pair shortest path query problem on interval and circular-arc graphs, instead of using the sophisticated technique, we propose simple parallel algorithms using only the parallel prefix and suffix computations and the Euler tour technique. Our preprocessing algorithms run in O(log n) t...

Using the notions of Q heaps and fusion trees developed by Fredman and Willard we develop a faster version of the fractional cascading technique while maintaining the linear space structure The new version enables sublogarithmic iterative search in the case when we have a search tree and the degree of each node is bounded by O log n for some constant where n is the total size of all the lists s...

We give improved space and processor complexities for the problem of computing, in parallel, a data structure that supports queries about shortest rectilinear obstacleavoiding paths in the plane, where the obstacles are disjoint rectangles. That is, a query specifies any source and destination in the plane, and the data structure enables efficient processing of the query. We now can build the d...

Planar graph navigation is an important problem with significant implications to both point location in geometric data structures and routing in networks. However, whilst a number of algorithms and existence proofs have been proposed, very little analysis is available for the properties of the paths generated and the computational resources required to generate them under a random distribution ...