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In recent years, the focus of cartographic research has shifted from the cartographic communication paradigm to the scientific visualization paradigm. With this, there has been a resurgence of cognitive research that is invaluable in guiding the design and evaluation of effective cartographic visualization tools. The design of new tools that allow effective visual exploration of spatial data and data quality information in a resource management setting is critical if decision-makers and policy setters are to make accurate and confident decisions that will have a positive long-term impact on the environment. The research presented in this dissertation integrates the results of previous research in spatial cognition, visualization of spatial information and on-line map use in order to explore the design, development and experimental testing of four interactive visualization tools that can be used to simultaneously explore spatial data and data quality. Two are traditional online tools (side-by-side and sequenced maps) and two are newly developed tools (an interactive "merger" bivariate map and a hybrid o f the merger map and the hypermap). The key research question is: Are interactive visualization tools, such as interactive bivariate maps and hypermaps, more effective for communicating spatial information than less interactive tools such as sequenced maps? A methodology was developed in which subjects used the visualization tools to explore a forest species composition and associated data quality map in order to perform a range of map-use tasks. Tasks focused on an imaginary land-use conflict for a small region of mixed boreal forest in Northern Alberta. Subject responses in terms of performance (accuracy and confidence) and preference are recorded and analyzed. Results show that theory-based, well-designed interactive tools facilitate improved performance across all tasks, but there is an optimal matching between specific tasks and tools. The results are generalized into practical guidelines for software developers. The use of confidence as a measure of map-use effectiveness is verified. In this experimental setting, individual differences (in terms of preference, ability, gender etc.) did not significantly affect performance.

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STARNET is a fiber optic based network which facilitates the interconnection of distributed Local Area Networks. Configured as a sixteen pointed star topology with a multiprocessor based controller at the center of the star (named the Central Switch). STARNET is capable of scheduling calls from users connected to User Access Nodes located at the points of the star. Messages are passed from one node to another through the Central Switch via duplex fiber optic lines connecting each node to the center. / This paper presents a multiprocessor based design of the User Access Node. The hardware and software structure is examined in depth, providing solid guidelines for the physical construction of the unit. The performances of statistical STARNET models using parameters obtained from the design (and three different Central Switch models) are plotted and compared for five different examples of external traffic. The model analysis gives an indication of the expected message delays, supporting the feasibility of the design.

The project investigated the problem of performance optimisation of computer systems at the systems level. It was ascertained that no generally accepted technique for approaching this problem exist. A theoretical approach was thus developed which describes the system, the workload and the performance in terms of matrices which are deduced from measured data. An attempt is then made to verify this theory by applying it to a real system in a controlled environment. A dummy workload is used and measurements are made on the computer system for various configurations. The results thus obtained are compared with the expected trends in system performance and conclusions are drawn which appear to verify the validity of the theory proposed. / Thesis (M.Sc.Eng.)-University of Natal, 1987.

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Web applications have become a large segment of the software development domain but their rapid rise in popularity has far exceeded the support in software engineering. There are many tools and techniques for web application development, but the developer must still learn and use many complex protocols and languages. Products still closely bind data operations, business logic, and the user interface, limiting integration and interoperability. This thesis introduces an innovative new presentation service to help web application developers create better applications faster, and help them build high quality web user interfaces. This service acts as a broker between web browsers and applications, adding value with programming-language independent object-oriented technology. The second innovation is a generic graphics applet (GGA) component for the web browser user interface. This light component provides interactive graphics support for the creation of business charts, maps, diagrams, and other graphical displays in web applications. The combination of a presentation service program (BUS) and the GGA is explored in a series of experiments to evaluate their ability to improve web applications. The experiments provide evidence that the BUS and GGA technology enhances web application designs.