On the World Wide Web, XML and Open Hypermedia Systems

Denilson Barbosa

University of Toronto
dmb@cs.toronto.edu

The World Wide Web (the Web, for short) was designed to support the creation
of and access to hypertext content, independently of computing
platforms. This would be accomplished by the use of a standardized language
for encoding content, the Hypertext Markup Language (HTML). The motivation
behind this effort was to enable the exchange of data by a group of
scientist and engineers, as their research progressed. A decade later, the
Web has become the most popular application and the driving force of the
biggest computer network ever built. It is now an independent entity and has
its own standards, protocols, applications and etiquette. It has also
evolved from a pure hypertext nature to provide access to multimedia
content, even to live streaming media.

Open Hypermedia Systems (OHS) has been an active research field for some
time. The main goal being to provide hypermedia content to a variety of
applications in a shared computing environment. When it comes to the Web,
the hypermedia community is divided: some researchers consider it the most
obvious example of an OHS, while others argue it does not even classify as a
hypermedia system, leave alone an OHS. Despite its popularity and success,
the Web has been criticized for lacking the ability to properly deal with
structures, which are, at least, as important as data in hypermedia
applications.

Recently, new standardization efforts have being carried out by the WWW
Consortium (W3C), which is the body that dictates what the Web is and will
be. Their goal is to enrich the semantics of the Web, providing better
hypermedia and structure awareness. There are many on-going efforts that
encompass different research disciplines in computer science. Notably, the
Extensible Markup Language (XML) has received considerable attention from
both academia and industry due to its capability of representing documents
with structured content. Not only a language, XML is a family of standards
that provide improved semantics to the Web.

In this work, instead of providing a tutorial in XML, we show how it helps
bridging the gap between the Web and OHS. We present, through an example,
the main problems in hypermedia authoring using current HTML technology, and
how they are addressed in the new framework. Particularly, we describe how
richly structured documents can be published and manipulated using an
XML-enabled query language (XSLT). Current alternatives for rendering XML
content are also compared. Next, we discuss how XML facilitates data
exchange among applications, and why this makes data integration
possible. Finally, we outline how traditional hypermedia development
methodologies can be tailored to take advantage of XML.