Scheduling queries to improve the freshness of a website

The WWW is a new advertising media in recent years where corporations utilize it to increase their exposure to consumers. For a very large website whose content is derived from some source database, it is important to maintain its freshness in response to changes to the base data. This issue is particularly signicant for websites presenting fast changing information such as stock exchange information and product information. In this paper, we formally dene and study the freshness of a website that is refreshed by scheduling a set of queries to fetch fresh data from the databases. Then, we propose several online scheduling algorithms and compare the performance of the algorithms on the freshness metric. Our conclusion is veried by empirical results. Keywords: Internet Data Management, View Maintenance, Query Optimization, Hard Real-Time Scheduling 1 Introduction The popularity of the World-Wide Web (WWW) has made it a prime vehicle for disseminating information. More and ..

Metadata for Photographs: from Digital Library to Multimedia Application

This paper describes the production of an educational multimedia CD-ROM about French rural houses and farms, and how to renovate them without losing their traditional features. The educational message is illustrated with many photographs of non-renovated or renovated houses, and made explicit through comments and descriptions associated with the photos. The paper focuses on the XML metadata describing the photos and the use of this metadata for the automatic generation of Web pages. We first report on the usability of the Dublin Core for interoperable photographs metadata, together with more detailed XML descriptions to support a specific multimedia application. We then show how to generate the Web pages by defining HTML document prescriptions which embed queries to the XML metadata, using Norfolk, a virtual document generator. The approach can be used in various applications ranging from personal virtual photo albums to complex virtual museum

Incremental Maintenance of Hypertext Views

Abstract A materialized hypertext view is a hypertext containing data coming from a database and whose pages are stored in HTML files. This paper deals with the maintenance issues required by these derived hypertext to enforce consistency between page content and database state. Here, hypertext views are defined as nested oid-based views over the set of base relations. An algebra is proposed, which is based on a specific data model and which allows to define views and view updates. A language has been defined, whose instructions allow to update the hypertext to reflect the current database state. Incremental maintenance is performed by a simple algorithm that takes as input a set of changes on the database and automatically produces the update instructions. The motivation of this study is the development of the Araneus WebBase Management System, a system that provides both database and Web site management. 1 Introduction The great success of the Web among user communities is imposing..