637 research outputs found
Scalability Analysis of Declustering Methods for Cartesian Product Files
Efficient storage and retrieval of multi-attribute datasets
has become one of the essential requirements for many data-intensive
applications. The Cartesian product file has been known as an effective
multi-attribute file structure for partial-match and best-match queries.
Several heuristic methods have been developed to decluster Cartesian
product files over multiple disks to obtain high performance for disk
accesses. Though the scalability of the declustering methods becomes
increasingly important for systems equipped with a large number of disks,
no analytic studies have been done so far.
In this paper we derive formulas describing the scalability
of two popular declustering methods Disk Modulo and Fieldwise Xor
for range queries, which are the most common type of queries.
These formulas disclose the limited scalability of the declustering methods
and are corroborated by extensive simulation experiments.
From the practical point of view,
the formulas given in this paper provide a simple measure
which can be used to predict the response time of a given range query
and to guide the selection of a declustering method
under various conditions.
(Also cross-referenced as UMIACS-TR-96-5
Signature Files: An Integrated Access Method for Formatted and Unformatted Databases
The signature file approach is one of the most powerful information storage and retrieval techniques which is used for finding the data objects that are relevant to the user queries. The main idea of all signature based schemes is to reflect the essence of the data items into bit pattern (descriptors or signatures) and store them in a separate file which acts as a filter to eliminate the non aualifvine data items for an information reauest. It provides an integrated access method for both formattid and formatted databases. A complative
overview and discussion of the proposed signatnre generation methods and the major signature file organization schemes are presented. Applications of the signature techniques to formatted and unformatted databases, single and multiterm query cases, serial and paratlei architecture. static and dynamic environments are provided with a special emphasis on the multimedia databases where the pioneering prototype systems
using signatnres yield highly encouraging results
On construction, performance, and diversification for structured queries on the semantic desktop
[no abstract
Extending functional databases for use in text-intensive applications
This thesis continues research exploring the benefits of using functional
databases based around the functional data model for advanced database
applications-particularly those supporting investigative systems. This is a
growing generic application domain covering areas such as criminal and military
intelligence, which are characterised by significant data complexity, large data
sets and the need for high performance, interactive use. An experimental
functional database language was developed to provide the requisite semantic
richness. However, heavy use in a practical context has shown that language
extensions and implementation improvements are required-especially in the
crucial areas of string matching and graph traversal. In addition, an
implementation on multiprocessor, parallel architectures is essential to meet the
performance needs arising from existing and projected database sizes in the
chosen application area. [Continues.
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