Databases Reference
In-Depth Information
12
Construction of Web Structures from
Heterogeneous Information Sources
Hiroyuki Kitagawa
Atsuyuki Morishima
Institute of Information Sciences and Electronics
University of Tsukuba
ABSTRACT
With the broad acceptance of the World Wide Web, the Web has been widely used for
publishing and disseminating information originally stored in various information
sources. They include databases, document repositories, and Web servers. In
constructing Web structures on top of the heterogeneous information sources, data
acquisition is an essential issue. Also, design of data layout on Web pages is another
important issue. A lot of work has been reported on the problem so far, and some
tools and systems are used in practical applications. In this article, we survey the
current approaches to this problem in the first part, and show our approach in the
second part. The current approaches to the problem can be classified into the program
development approach, the template-based approach, and the mediation approach.
In the first approach, application programs to acquire data and to generate Web
pages are developed from scratch, and they are invoked through CGI, Servlet, and/or
Web server API. In the template-based approach, some kinds of layout templates
with scripts and queries are used to specify the data acquisition and data layout
simultaneously. In the mediation approach, a common mediation data model is
introduced to specify layout-independent logical data acquisition or data integration.
In this article, we mainly explore the mediation approach, since this approach is most
promising in the context of large-scale Web structure construction. We give an overview
of the current technology related to this approach from a number of important design
viewpoints. The second part of this article explains some details of our approach. It
takes the mediation approach. The common data model is based on nested relations
and ADTs, and interactive visual authoring facilities are provided for data layout
specification.
1
Introduction
With the broad acceptance of the World Wide Web, the Web has been widely used
for publishing and disseminating information originally stored in various
information sources. They include databases, document repositories, and Web
181
