Databases Reference
In-Depth Information
11
XML Databases
Masatoshi Yoshikawa
Nara Institute of Science and Technology
ABSTRACT
With rapid development of standards and supporting software tools, XML (extensible
Markup Language) is becoming pervasive as the next generation Web language. Since
XML is widely attracting attention as a language for describing data as well as
structured documents, XML's role in Web databases is crucial. In this paper, we describe
major research issues on the interrelation between XML and database technologies.
First, we present the data model of XML1.0. Then, we provide an overview of query
languages for XML. Next, we describe various approaches to the storage and retrieval
of XML data. In particular, we focus on alternative methods of mapping XML data
into relational database schemas. Fast search of XML data requires special physical
data organizations. Finally, we present indices for XML data, and show how each
index support fast retrieval for representative query operations.
1
Introduction
XML (eXtensible Markup Language) is becoming widely used as a standard meta
language to represent structured documents and data on the Web. One of the
major reasons for the wide acceptance of XML is its independence from platforms,
operating systems, network protocols and applications. The wide dissemination
of the Web and the advent of universal data format such as XML have a crucial
impact on the research of databases. The research issues raised by the
interrelationship between XML and database can be summarized in the following
two categories:
1.
Database management systems as repositories for XML documents:
Since XML has now become a standard language, XML documents will be
produced in wide area of applications. Efficient and flexible management
of large volume of XML documents requires the functionalities of DBMSs
such as fast retrieval and update, integrity constraints enforcement,
concurrency control, access right control, and version management. An
important issue is how conventional DBMSs or text indices can be used, or
can be adapted to cope with large volume of XML data. Unlike many
other types of data stored in traditional databases, XML documents has
logical structures. The development of techniques to exploit such logical
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