MPhil Thesis Defence


"The Development of The Nested Relational Sequence Model to Support XML
Databases"

By

Mr. Ho-Lam Lau


Abstract

XML is becoming a standard for representing and exchanging data on the
Web. As a result, the quantity of XML documents being processed by
web-based information systems has been rapidly increasing. It is generally
accepted that there is a need to apply existing database technology for
storing and retrieving XML data. However, due to the fact that XML is
inherently hierarchical in structure, which is characterized by complex
nested tags in an XML document, XML data does not easily fit into the
underlying data model of common DBMSs. We propose an XML data model, the
Nested Relational Sequence Model (NRSM), which is an extension of the
Nested Relational Data Model in order to handle XML data. Within the NRSM,
the methods for mapping valid and well-formed XML documents into Nested
Relational Sequence relations (NRS relations)are discussed. This thesis
demonstrates that the processes of retrieving XML documents and extracting
their corresponding DTD from NRS relations are natural and
straightforward, since these processes are reversible and
information-preserving. A set of algebraic operations pertaining to the
NRSM, called NRS operations, which allows the manipulation of XML
documents through queries imposed on  NRS relations is formally defined.
We demonstrate the NRS operations and show through examples how XML
queries can be formulated in a straightforward manner. Finally, we
implemented the NRSD System that is built with NRSM as the underlying data
model. NRS databases is a middleware system between the users and the
relational DBMS, it allows users to perform queries in a more natural
ways.


Date:			Wednesday, 28 August 2002

Time:			9:15a.m.-11:15a.m.

Venue:			Room 1505
			Lifts 25-26

Committee Members:		Dr. Wilfred Ng (Supervisor)
			Dr. Andrew Horner (Chairman)
			Dr. David Rossiter



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