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The critical interface between learners and computer-based learning materials is the screen. If the display of learning is not effective then learning will be hindered. Screen design is therefore an important element in the design of computer-based learning. This research investigated the three fundamental screen design elements of text, colour and graphics. A review of literature, experimental design and a limited survey of computer-based learning materials provided the background for this research. The experimental materials reflected the results of the review and survey by using representative subjects, providing a learning focus and employing computerbased materials. Two experiments were undertaken. The Colour and Graphics experiments considered the effects of a number of variables on learners' behaviour which included: the use of colour; the size and type of graphics; the learner's prior knowledge of tutorial subject; and the complexity of the display. The results of this research showed that colour is a powerful motivating force as long as it is not used excessively. This was identified as the use of more than seven colours. Graphics can be used more extensively in current computer-based learning materials and users preferred representational graphics occupying a quarter to a half of the screen. However, learners were not prepared to make the effort to either use analogical graphics to make links with their prior knowledge or to extract information contained in the structure and form of logical graphics. Subjects were motivated by representational graphics. Learners' behaviour in relation to the various screen displays they encountered was affected by their prior knowledge of the tutorial content. This was apparent in their choice of options (additional modules) within the tutorial, their methods of interacting with the material and their responses to individual displays.

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This thesis develops an approach that supports multidisciplinary practice in requirements engineering. It is argued that multidisciplinary requirements engineering practice is ineffective, and some specific problems for multidisciplinary practice are identified. It is also suggested that the incommensurability of conflicting paradigms is an underlying cause of the problems in multidisciplinary practice, and a number of criteria for support to overcome such problems are proposed. A form of methodological support, which it is claimed may help overcome some of the problems associated with multidisciplinary practice in requirements engineering, is developed. This methodological support takes the form of a dialectic process, and its associated products, which is conceptualised and then operationalised. As an illustration of the methodological support offered to multidisciplinary practice, the operationalisation of the dialectic process is applied to requirements constructed by the use of two different requirements engineering techniques from two different disciplines (representing two different paradigms), in the domain of Accident and Emergency healthcare. Finally, the application of the operationalisation of the dialectic process is assessed with respect to the criteria for support for multidisciplinary practice proposed earlier, and this assessment is used to reconceptualise the dialectic process. The limitations of the research are identified, and possibilities for future work proposed. This thesis is aimed primarily at the requirements engineering community, and in particular the practising requirements engineer. It makes two contributions to knowledge supporting the practices of requirements engineering. First, the thesis contributes two types of substantive discipline knowledge: an explanation of why multidisciplinary practice in requirements engineering is problematic; and the proposal of criteria for support to allay the difficulties of multidisciplinary practice. It is suggested that these criteria might be used in the development of new types of support to overcomes such difficulties, or in the assessmment of new requirements engineering techniques that claim to address multidisciplinary practice. Second, the thesis contributes methodological knowledge in the form of a dialectic approach that offers a new way of reasoning about requirements engineering. This methodological knowledge takes two forms: a generic dialectic approach that might be applied by requirements engineering practitioners to requirements, generated by a wide range of requirements engineering techniques, representing alternative paradigms; and a specific instantiation of the dialectic approach using the MUSE method and the Grounded Theory method, that might be used in its current form by requirements engineering practitioners to support their own multidisciplinary practice.

The number of network users is expected to triple between 1998 and 2002 (Cullinane, 1998). While a vision of the future Internet offers the potential to break traditional barriers in communications and commerce, the current level of service does not satisfy the requirements of many users (Network Reliability Steering Committee, 1998, Cullinane, 1998). This thesis is concerned with users' perceptions of Quality of Service (QoS), and their attitudes to charging mechanisms applied to wide-area networks. Whilst the majority of research in this area has been conducted from a technical point of view, studies addressing issues of QoS and charging from a users' perspective are limited. The aim of this research was to investigate the latter issue to provide a more complete and integrated perspective on QoS and charging in the user-network system. The thesis first addresses previous work that looks at QoS and charging, establishing a justification for the new research. This part of the thesis concludes that, whilst part of our understanding of QoS requirements can be explained by technical and economic paradigms, additional research is required to examine the perceptions and concomitant behaviour of users. The methodology employed is outlined in relation to obtaining this objective. The second part of the thesis details work undertaken. This work has made the following main contributions: *Developed a set of conceptual models that describe users' perceptions of network QoS. *Shown that these models can be used to predict users' behaviour in different contexts by capturing subjective evaluations of QoS. * Shown how a combination of established and new methods can be successfully applied in capturing and assessing users' perceptions of QoS. *Shown how the new data relates to technical and econometric research. *Provided concrete examples of how the new research can inform network systems design. The work documented in this thesis has implications for user-centred, technical and econometric research. This thesis therefore contributes, not only to the field of HCI to which it is most closely related, but provides guidelines that can be used by econometricians and network designers. The research from all three of these perspectives is concerned with the efficient function of network resource allocation systems. The work documented in this thesis has suggested how it is possible to integrate these perspectives to provide valued levels of QoS to users.

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