Hybrid Approach for the Maintenance of Materialized Webviews

In this paper, we have developed an approach to specify when updating materialized webviews. A webview is a web page that is automatically constructed from a structured database. We have introduced a new update policy called “early ondemand” update which is based on the user preferences. Then we have combines this policy with the on-demand one to update the materialized webviews. Our experiments showed that the proposed hybrid approach guarantees strong consistency of data and allows reducing latency of updating webviews. In addition, they prove that our solution decreases the server overload (access+ update cost) significantly better that the on-demand and the immediate policies

Online View Selection for the Web

View materialization has been shown to ameliorate the scalability problem of data-intensive web servers. However, unlike data warehouses which are off-line during updates, most web servers maintain their back-end databases online and perform updates concurrently with user accesses. In such environments, the selection of views to materialize must be performed online; both performance and data freshness should be considered. In this paper, we discuss the Online View Selection problem: select which views to materialize in order to maximize performance while maintaining freshness at acceptable levels. We define Quality of Service and Quality of Data metrics and present OVIS(theta), an adaptive algorithm for the Online View Selection problem. OVIS(theta) evolves the materialization decisions to match the constantly changing access/update patterns on the Web. The algorithm is also able to identify infeasible freshness levels, effectively avoiding saturation at the server. We performed extensive experiments under various workloads, which showed that our online algorithm comes close to the optimal off-line selection algorithm. Also UMIACS-TR-2002-2

Effectively Maintaining Single View Consistency in Web Warehouses

Web warehouse provides high availability and efficiency by utilizing materialized webviews, which should be refreshed in time to keep freshness. During the refreshing, the consistency between a webview and its base data, which is formally named single view consistency (abbreviated as SVC), must be guaranteed. Since the base data changes in a web warehousing environment do not propagate from data sources to the information consumers, which is far different from the case in the traditional data warehouses, we must pursue new maintenance methods. In this paper we first introduce the definition for SVC, and then we present an algorithm RCA to keep SVC as well as an effective base data change detection method SAA. We illustrate that RCA and SAA can guarantee SVC and they are effective in the web environment. ? 2005 IEEE.EI

The Design of a Web Snapshot Management System for Decision Support Applications

Database snapshots that are defined and/or delivered via the Web are called web snapshots. This paper addresses the requirements for web snapshot management. A web snapshot management system is proposed; its architecture and functions of the major components are described; new commands are defined to perform web snapshot management activities

The Extended Commands for the Management of Database Snapshots for Internet Decision Support Applications

Database snapshots have been an effective way of supporting decision support applications, and will continue to play an important role in providing data in an Intranet decision support environment. This paper discusses the special characteristics of the database snapshot management in an Intranet decision support environment, review the major components involved in the management of snapshots, and then define new commands for the management of snapshots in this environment

Greedy Selection of Materialized Views

Greedy based approach for view selection at each step selects a beneficial view that fits within the space available for view materialization. Most of these approaches are focused around the HRU algorithm, which uses a multidimensional lattice framework to determine a good set of views to materialize. The HRU algorithm exhibits high run time complexity as the number of possible views is exponential with respect to the number of dimensions. The PGA algorithm provides a scalable solution to this problem by selecting views for materialization in polynomial time relative to the number of dimensions. This paper compares the HRU and the PGA algorithm. It was experimentally deduced that the PGA algorithm, in comparison with the HRU algorithm, achieves an improved execution time with lowered memory and CPU usages. The HRU algorithm has an edge over the PGA algorithm on the quality of the views selected for materialization

An Initial Design of a Website Snapshot Management System

A website snapshot is the state of a web site at a specific point in time. It supports applications that require historical data. Most website snapshots are created by making a copy of the website. These date-time stamped physical snapshots are unable to satisfy users’ need for snapshots of different snapshot times. This research proposes a scheme that is able to create website snapshots that meet any snapshot time requirements by recording changes to a website in a log. For web pages producing dynamic content from a database, this scheme will allow the pages to access a database snapshot at the website snapshot time

The Design of a Web Document Snapshots Delivery System

A web document snapshot is a point-in-time capture of its code and the resulting presentation of executing the code. It is used as a way of electronically preserving historical information published in web documents enabling an organization to audit a web document’s contents at a point in the past and perform business analyses with historical information recorded in it. It is also an archived copy of a web document when it is changed. This research develops a system to deliver snapshots of a web document’s static and dynamic contents when it is requested. The system consists of a Database Snapshot Manager for providing database snapshots and a Web Document Snapshot Manager for providing web document snapshots. Algorithms supporting the two managers are presented