This research represents an investigation into user acceptance of computer systems. It starts with the premise that existing systems do not fully meet user requirements, and are therefore rejected as 'difficult to use'. Various problems and influences affecting user acceptance are identified, and improvements are suggested. Although a broad range of factors affecting user acceptance are discussed, emphasis is given to the impact of actual computer software. Initially, both general and specific user interface software influences are examined, and it is shown how these needs can be met using new software technology. A new Intelligent Interface architecture model is presented, and comparisons are made to existing interface design approaches. Secondly, the role of empirical work within the field of Human Computer Interaction is highlighted. An investigation into the usability and user. acceptance of a large working library database system is described, and the results discussed. The role of Systems Analysis and Design and its effect upon user acceptance is also explored. It is argued that despite improvements in interface technology and related software engineering techniques, a software application is also a product of the Systems Analysis and Design process. Traditional Systems Design approaches are examined, and suitable improvements suggested based upon experience with emerging separable software architectures. Thirdly, the research proceeds to examine the potential of Quantitative User Modelling, and describes the implementation of an example object oriented Quantitative User Model. This is then evaluated in order to determine new knowledge, concerning the major issues surrounding the potential application of user modelling to interface design. Finally, attention is given to the concept of interface and application separation. An object oriented User Interface Management System is presented, and its implementation in the Smalltalk 80 programming language discussed. The proposed User Interface Management System utilises a new software architecture which provides explicit user interface separation, using the concept of a Pluggable View Controller. It also incorporates an integrated design Tool-set for Direct Manipulation interfaces. The proposed User Interface Management System and software architecture represents the major contribution of this project to the growing body of Human Computer Interaction research. In particular, the importance of explicit interface separation is established, and the proposed software architecture is critically evaluated to determine new knowledge concerning the requirements, constraints, and potential of proper user interface separation. The implementation of an object oriented Part Hierarchy mechanism is also presented. This mechanism is related to the proposed User Interface Management System, and is critically evaluated in order to add to the body of knowledge concerning object oriented systems.

This thesis examines, conceptually and empirically, the educational role of microcomputers in primary schools. The first part of the thesis is, in the main, theoretical. It is concerned with making more explicit the meaning of the term 'computer education' and the kinds of activities to which it may legitimately refer. The first chapters seek to substantiate the argument that, in essence, 'computer education' is an attempt to use computers in ways which foster and promote the quality of the educational processes provided by schools. Having considered computer education from a theoretical perspective, it is then explored empirically. An interpretive research methodology was utilized. The methods used to gather data were thus mostly qualitative, rather than quantitative. Case studies were undertaken to illuminate the ways in which computer education was interpreted in three primary schools. Attention focused on the educational values implicit in policy and practice and on identifying correspondence and discrepency between how computers were used and the educational philosophies espoused by individual teachers and schools. The empirical research revealed that imprecise, non-explicit and largely unarticulated intentions were being pursued by teachers in their employment of computers. No particular educational rationale was being explicitly adopted, even though, some close affinity between educational values and classroom practice would seem to be essential if the notion of 'computer education' is to have any real meaning. However, the conclusion of this thesis is not to doubt the importance of microcomputers in primary education. Rather, it is to suggest that fundamental questions about the educational purpose of computers need to be more rigorously addressed if computers are to be integrated into the curriculum of the future in ways which hold out some promise of improving the quality of educational experiences offered by primary schools.

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With the availability of fast microprocessors and small-scale multiprocessors, internode communication has become an increasingly important factor that limits the performance of parallel computers. Essentially, message-passing parallel computers require extremely short communication latency such that message transmissions have minimal impact on the overall computation time. This thesis concentrates on issues regarding hardware communication latency in single-hop reconfigurable networks, and software communication latency regardless of the type of network. The first contribution of this thesis is the design and evaluation of two different categories of prediction techniques for message-passing systems. This thesis utilizes the communications locality property of message-passing parallel applications to devise a number of heuristics that can be used to predict the target of subsequent communication requests, and to predict the next consumable message at the receiving ends of communications. Specifically, I propose two sets of predictors: Cycle-based predictors, which are purely dynamic predictors, and Tag-based predictors, which are static/dynamic predictors. The performance of the proposed predictors, specially Better-cycle2 and Tag-bettercycle2, are very well on the application benchmarks studied in this thesis. The proposed predictors could be easily implemented on the network interface due to their simple algorithms and low memory requirements. As the second contribution of this thesis, I show that majority of reconfiguration delays in single-hop reconfigurable networks can be hidden by using one of the proposed high hit ratio predictors. The proposed predictors can be used in establishing a communication pathway between a source and a destination in such networks before this pathway is to be used. This thesis' third contribution is the analysis of a broadcasting algorithm that utilizes latency hiding and reconfiguration in the network to speed the broadcasting operation. The analysis brings up closed formulations that yields the termination time of the algorithms. The thesis' fourth contribution is a new total exchange algorithm in single-hop reconfigurable networks. I conjecture that this algorithm ensures a better termination time than what can be achieved by either of the direct, and standard exchange algorithms. The fifth contribution of this thesis is the use and evaluation of the proposed predictors to predict the next consumable message at the receiving ends of communications. This thesis contributes by claiming that these message predictors can be efficiently used to drain the network and cache the incoming messages even if the corresponding receive calls have not been posted yet. This way, there is no need to copy the early arriving messages into a temporary buffer. The performance of the proposed predictors, Single-cycle, Tag-cycle2 and Tag-bettercycle2, on the parallel applications are quite promising and suggest that prediction has the potential to eliminate most of the remaining message copies. / Graduate

This thesis describes the evaluation of four operating systems for microcomputers. The emphasis of the study is on the suitability of the operating systems for use in real-time applications, such as process control. The evaluation was performed in two sections. The first section was a quantitative assessment of the performance of the real-time features of the operating system. This was performed using benchmarks. The criteria for the benchmarks and their design are discussed. The second section was a qualitative assessment of the suitability of the operating systems for the development and implementation of real-time systems. This was assessed through the implementation of a small simulation of a manufacturing process and its associated control system. The simulation was designed using the Ward and Mellor real-time design method which was extended to handle the special case of a real-time simulation. The operating systems which were selected for the study covered a spectrum from general purpose operating systems to small, specialised real-time operating systems. From the quantitative assessment it emerged that QNX (from Quantum Software Systems) had the best overall performance. Qualitatively, UNIX was found to offer the best system development environment, but it does not have the performance and the characteristics required for real-time applications. This suggests that versions of UNIX that are adapted for real-time applications are worth careful consideration for use both as development systems and implementation systems.

No description available.

Continuing advances in hardware and in software applications are pushing traditional operating systems beyond their limits. This is largely due to the fact that these advances, and their associated requirements, were not foreseen at operating system design time. This becomes particularly apparent with multimedia applications, whose demands for guaranteed quality of service differ considerably from those of most traditional applications. To ensure that many future requirements will be met, along with many existing demands, one solution is to allow applications to customize their operating system throughout its life-time. However, opening up an operating system to application-initiated changes can compromise the integrity of the system, suggesting the need for a security model. Like any other aspect of a customizable system, such a security model should be securely customizable, too. Therefore, this dissertation introduces MetaOS, a securely- and dynamically-customizable operating system which has a securely- and dynamically-customizable security model. MetaOS employs four types of building blocks: meta-levels, meta-spaces, meta-objects, and meta-interfaces. Meta-levels localize customizable system services. Meta-spaces act as firewalls which prevent custom alterations from affecting unrelated meta-spaces and their applications. Meta-objects help to modularize meta-spaces into smaller, easier-to-maintain components. Finally, meta-interfaces provide the heart of the secure customizing model. MetaOS meta-interfaces are strictly divided into declarative and imperative interfaces, providing a basis on which to distinguish between calls which only affect the invoking application (i.e., local-effect calls), and calls which could affect other applications as well (i.e., meta-space-wide-effect calls). By giving free access to the former, but limiting access to the latter, a basic balance between flexibility and security can be struck. Additional flexibility is achieved by allowing new local and meta-space-wide-effect calls to be added dynamically, by permitting untrusted applications to negotiate changes with trusted meta-space managers, and by allowing untrusted applications to migrate to cloned meta-spaces and alter them as necessary. / Graduate

M.Sc. (Computer Science) / Please refer to full text to view abstract

The use of mobile phones and other mobile devices are becoming widespread and almost all of these mobile devices have some sort of mobile Internet access. Due to the increase in mobile Internet usage, many websites need altering in order to become mobile compatible. Creating a mobile compatible version of a website is challenging due to formatting and capability restrictions imposed by the mobile device. Currently, one of the popular methods of creating a mobile compatible website involves the creation of a new, dedicated mobile version of the website. However, this approach can prove to be expensive, and repetitive, since a fully functional desktop version of the website often already exists. A second method involves the use of a transformation proxy to transform the traditional website into a mobile compatible version. This research develops a transformation framework that enables a web developer to create a single set of source files that can be used to render output compatible with both traditional and mobile devices. In developing this framework, capabilities and restrictions of the mobile device were examined. Furthermore, current mobile web development guidelines and best practices were discussed. This resulted in the development of a method to identify and outline areas of a traditional website for transformation into a mobile friendly format. Furthermore, a transformation engine that allowed processing of the traditional website into a mobile compatible website was developed. This transformation engine extracted the outlined areas, and rendered the extracted content, all while maintaining the website’s original functionality. The development of a prototype verified that the transformation concepts are valid, and provided for the development of guidelines and recommendations. The development of a framework to enable the web developer to create a website once, and enable it to adapt its output for mobile devices, will have a positive impact on the development of content for the mobile web.