Nabil I. Hachem

Integrating the rewriting and ranking phases of view synchronization

Material&d views (data warehouses) are becoming increasingly important in the context of distributed modem environments such as the World Wide Web. Information sources (I%) in such an environment may change their capabilities (schema), causing a data warehouse to become undefined. This process to evolve (rewrite) view queries after capability changes of ISs is referred to ss view synchronization. Current view synchronization algorithms generate a potentially large number of valid solutions for the rewriting of a view query and according to our analysis in this paper have high complexity (in O(n!)). We propose to reduce this complexity by representing the synchronization problem as a graph traversal problem. Once this mapping has been applied, the problem can be reduced to a single-source shortestpath problem in graphs, which can be solved with O(n3) complexity using the Bellman-Ford algorithm.

A DBMS architecture for global change research

The goal of this research is the design and development of an integrated system for the management of very large scientific databases, cartographic/geographic information processing, and exploratory scientific data analysis for global change research.The system will represent both spatial and temporal knowledge about natural and man‐made entities on the eath’s surface, following an object‐oriented paradigm. A user will be able to derive, modify, and apply, procedures to perform operations on the data, including comparison, derivation, prediction, validation, and visualization. This work represents an effort to extend the database technology with an intrinsic class of operators, which is extensible and responds to the growing needs of scientific research.Of significance is the integration of many diverse forms of data into the database, including cartography, geography, hydrography, hypsography, images, and urban planning data. Equally important is the maintenance of metadata, that is, data about the data,...

A visual programming environment for supporting scientific data analysis

The authors research on a conceptual model for scientific data analysis concludes that traditional computational and environmental support is insufficient. They believe an integrated system that provides users with the ability to manage data, processes, and experiments as well as program data analysis tasks is necessary. The development of GaeaVE, a visual environment for a scientific database management system for global change research, is described. The components of the environment consist of a browser, a visual language editor for processes and experiments, and a data viewer.<<ETX>>

The average height of a node in the BANG abstract directory tree

Abstract The abstract logical data structure for the BANG file directory is a multiway tree structure with one node for each bucket in the file. Under assumptions of “perfect hashing” or “growth on data principle”, we model the growth of the tree. The average cost for search and insertion is found to be logarithmic in the file size. The order constant is small and depends on the capacity of a bucket. Simulation confirms the analytic results. Similar assumptions should be applicable to the analysis of other multi-dimensional file structures.

Machine vision detection of the high points on small, curved, shiny things

In this paper we discuss how to design a practical height gauging system based on the structured lighting approaches described. We show how some of the system limitations caused by the illumination and observation geometry affect component specifications. Examples of a machine vision inspection applications designed using these design principles is presented and analyzed. Finally, we discuss methods to extend this method.

Intelligent data analysis systems

A variety of approaches to the intelligent analysis of complex manufacturing data have been described in the literature. A comparative analysis of these systems reveals underlying similarities in their functional organizations. This leads to the development of a general functional model for intelligent data analysis (IDA).This article describes the various data analysis systems studied, the general model for IDA, and the implementation of a demonstration IDA system. The implementation serves to demonstrate the feasibility of this approach, and provides directions for further research.

An approximate analysis of the performance of extendible hashing with elastic buckets

Abstract This paper extends the analysis of extendible hashing to cover partial expansions with elastic buckets. Although previous studies of elastic buckets can be adapted to extendible hashing, the approach taken here provides another view to the problem. We provide a correspondence between fixed bucket capacities and elastic buckets. Furthermore, the results are based on easy and straightforward approximations.

A direct algorithm for computing the transitive closure of a two-dimensionally structured file

It is well-known that the computation cost to find the transitive closure (TC) of a graph stored as an adjacency matrix is the same, to within a constant factor, as matrix multiplication. In this paper, we present a new TC algorithm based on double hashing and two-dimensionally organized files. We show that, when using this algorithm, the computation and i/o costs of finding the TC of a database relation is like that of performing a relational composition operation. For sparse closures, sparse compositions will be performed, which may be significantly more thrifty than the corresponding matrix operations, which must be at least O(n2), and for which most algorithms are O(n3).