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    Applying bifocal displays to data visualisation : a dissertation presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Computer Science at Massey University, New Zealand
    (Massey University, 1995) Leung, Ying Keung
    Rapid advances in communications and computer technologies in recent years have provided users with greater access to large volumes of data from computer-based information systems. The issue of the relatively small window through which an information space can be viewed brings with it two associated problems: presentation and navigation. This research is based on an approach called the Bifocal Display proposed by Spence and Apperley to address these inherent difficulties common in large information spaces in modern computing environments. The essence of this presentation technique is to provide the user with detailed local content as well as a global context to facilitate navigation. In this research, the original one-dimensional Bifocal Display concept has been extended in two-dimensional form to deal with two fundamental types of large information spaces: those with a high information density, for example, large databases and spreadsheets, and those with inherent spatial relationships, such as topographic maps and networks. An experimental study has been carried out to study the usability of the Bifocal Display and other presentation techniques based on various implementations of the London Underground map. Results have shown that the Bifocal Display is a usable and effective approach for the presentation of large information spaces. Presentation techniques can be broadly classified into distortion-oriented and non-distortion-oriented; the former generally requires more computational resources than the latter. With the increasing processing power of personal computers, researchers have developed a variety of novel distortion-oriented presentation techniques. Unfortunately, the distorting appearance resulting from the application of these techniques, coupled with the growing number of new terminologies used by researchers, has caused some confusion to the graphical user interface designer. A taxonomy of distortion-oriented techniques based on their magnification functions has been proposed to facilitate the identification of the similarities and differences of these techniques. A conceptual model has also been put forward to unveil the underlying principles which govern their operations. Despite the variety of novel presentation techniques currently available, the choice of a technique in a particular application remains very subjective; there is a general lack of selection guidelines or methodologies. An evaluation framework E3 has been developed to provide a basis for the comparison of different presentation techniques, given the nature and characteristics of the data to be presented, and the interpretation required. E3 focuses on three aspects of graphical data presentation: expressiveness, efficiency and effectiveness. This framework lays the foundation for the development of a set of metrics to facilitate an objective assessment of presentation techniques. A general visualisation tool, the InfoLens, has been designed based on the theoretical framework of this research. The design of the InfoLens has further demonstrated that the Bifocal Display is an effective approach to visualising large information spaces.
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    Dialogue activation : an approach to user centred constructional modelling of direct manipulation interfaces : a dissertation presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University
    (Massey University, 1995) Anderson, Paul Stuart
    Early stages in the development of interfaces involve the construction of models that aid interface analysis prior to construction. These behavioural models generally take a user-centred perspective. In contrast, subsequent implementation models tend to take a system-centred view of the interface. As a consequence of this change in viewpoint, the task of translating an analysis model into its implementation equivalent is extremely difficult. This thesis proposes a constructional modelling approach for direct manipulation user interfaces (DMUI) that takes a user action viewpoint. Based on a hierarchy of dialogue groups and the notion of dialogue activation, sequence and concurrency within the interface can be described. Dialogues can be in one of two possible states, active or inactive. An active dialogue is one with which the user is able to interact. A dialogue becomes active only if its parent is active, and it receives one of a set of possible activating events. A second set of deactivating events can also exist. In this way a dialogue can be specified in terms of both a user's actions and the sequences in which those actions may be carried out. Dialogue Activation Language (DAL), a language for describing such models is developed, and shown to be applicable to a range of interaction styles. An architecture capable of implementing the dialogue activation model is proposed, and a user interface development system (PIPS), based on this architecture and using DAL is described. It is argued that DAL takes the same view of an interface as would be used in its initial analysis, and as a consequence, facilitates the translation of these early interface models into working prototypes. In addition, it is proposed that taking the DAL approach to modelling DMUI allows great flexibility in describing interaction and encourages experimentation with entirely new interaction styles.
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    The development of a visual language for image processing applications : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Computer Science at Massey University, Palmerston North, New Zealand
    (Massey University, 1992) Ngan, Phillip Michael; Ngan, Phillip Michael
    The research described in this thesis is based on the hypothesis that computer support for the heuristic development of image processing algorithms can be improved by the provision of a human-computer interface that is suited to the task. Current interfaces are largely text based and are not specifically designed to provide this support. It is suggested that an interface incorporating aspects of menu-based, direct manipulation, and visual languages, can provide the necessary support. The research of this thesis begins with an analysis of the task of image processing algorithm development. It is found that in development, algorithms are more appropriately viewed as data-oriented networks of imaging operations than as process-oriented lists. The representation of algorithms in most current interfaces, particularly in text based systems, do not clearly convey the multi-threaded data paths in an algorithm. However, a data-oriented representation expresses such parallel paths clearly and naturally. The second finding of the analysis is that human designers employ a set of problem solving strategies or heuristics in the interactive development of algorithms. These strategies include the top-down decomposition of the imaging task, the identification and focus of critical sub-goals, the progressive refinement of an algorithm, and the modification of existing algorithms. These heuristics are used implicitly in the development of algorithms, but the ease with which they are used in text based interfaces is restricted by the lack of appropriate interactive facilities. An evaluation of interface techniques suggests that an interface that combines aspects of menu-based, direct manipulation, and visual languages, can support the required interaction for the heuristic development of algorithms. The required data-flow view can be provided by an iconic data flow language. Such a representation is highly visible, and can be interpreted by a user at a glance. Quick and convenient specification and editing of a data flow network can be performed via direct manipulation interaction facilities. The search for suitable operations can be facilitated by menu systems. On the basis of the arguments for the adoption of a data-flow representation of algorithms, a problem solving approach to algorithm development, and highly interactive facilities, a software package, called OpShop, has been implemented. Examples which compare OpShop to text based systems show that four major tasks involved in algorithm development are better supported with the new interface. These tasks are the visualisation of multi-threaded data paths, the interactive experimentation with algorithm parameters, the modification of algorithm topology, and the comparison of alternative algorithms. In these examples, the OpShop software represents the tangible outcome of the design for an interface that specifically supports the heuristic development of image processing algorithm.