Degree Name

Doctor of Philosophy


Department of Computer Science


This thesis addresses a particular aspect of the retrieval of information from a wide variety of global information sources. This aspect is based on the model of a user working on a topic of interest over an extended period of time. During the time period, information is accessed, assembled, and correlated to satisfy the user's view of the topic.

The objective of the research described in this thesis is to ensure that the information accessed by the user over the extended period of time is both complete and consistent from the user's viewpoint.

A fundamental problem is achieving such consistency is that the information sources, typically databases, or data files, are independently controlled with their own individual viewpoints. Changes in content, structure, and access can therefore be made without the direct knowledge of the user.

In investigating this problem a number of current implementations of Heterogeneous Distributed Database Systems (HDDS) have been evaluated, including WAIS, ANSAware, and DATAPLEX. The mechanisms available in such systems do not address the requirements of the problem outlined in this thesis. A new set of mechanisms have been researched and implemented on a testbed as the central part of this thesis in order to match the requirements

The core of this testbed is a workstation-based interface for the user termed the Computer Software Interface (CSI). The CSI has been implemented to demonstrate that the set of mechanisms proposed are viable. One major aspect of the CSI has been the design and development of a local working environment for the user, and the associated theoretical proof needed to demonstrate that successful and complete access of this environment may be performed.

The thesis demonstrates, both theoretically and practically, how the user may be presented with consistent data from independent data sources over an extended time period.