The growth of the World Wide Web has in large part been made possible by the technologies that power it. These are the Web servers and Web browsers that many take for granted. Each has evolved to support the changing needs of users of the WWW from simple static text to highly interactive and dynamic multimedia. The Web servers, in particular, have evolved into a spectrum of different technologies to support what are now known as Web applications. These are usually installed and accessed through a Web server. Security is a problem in Web server environments and therefore the Web servers are usually run as an un-privileged user. Performance is another problem as some of these technologies require re-initialization of the execution environment with every subsequent request. These security and performance shortcomings have been dealt with by numerous Web application technologies. Most of these technologies are language-centric and seek solutions to the security and performance shortcomings independently of each other. The universal Web application server is proposed as an alternative solution addressing the security, language dependence and performance shortcomings of existing technologies. It has support for multiple authors in a secure environment with support for multiple implementation technologies (languages) using persistent interpreters to enhance performance. Test results from the performance evaluation show that the introduction of the layers of processing contributes a small percentage to the total request processing time and that the universal Web application server can perform comparably to other Web application servers. Tests with twenty users also showed that packaging and deploying Web applications in the universal Web application server is an easy and viable approach. Moreover, the installation of PhpBB2 in the universal Web application server demonstrates that it can be used with realistic Web applications. A universal Web application server that provides an efficient, secure and language independent environment has been developed and thoroughly evaluated demonstrating that a Web application server that addresses the shortcomings of existing technologies is feasible.

Computer scientists must align social and technical factors for communication technologies in developing regions yet lack a framework to do so. The novel Softbridge framework comprises several components to address this gap. The Softbridge stack abstraction supplements the established Open Systems Interconnect model with a collection of technical layers clustered around 'people' issues. The Softbridge stack aligns the technological design of communication systems with awareness of social factors characteristic of developing regions. In a similar fashion, a new evaluation abstraction called Quality of Communication augments traditional Quality of Service by considering socio-cultural factors of a user's perception of system performance. The conceptualisation of these new abstractions was driven by long-term experimental interventions within two South African digital divides. One field study concerned communication bridges for socio-economically disadvantaged Deaf users. The second field study concerned a wireless telehealth system between rural nurses and doctors. The application domains were quite different yet yielded similarities that informed the Softbridge and Quality of Communication abstractions. The third Softbridge component is an iterative socially aware software engineering method that includes action research. This method was used to guide cyclical interventions with target communities to solve community problems with communication technologies. The Softbridge framework components are recursive products of this iterative approach, emerging via critical reflection on the design, evaluation and methodological processes of the respective field studies. Quantitative and qualitative data were triangulated on a series of communication prototypes for each field study with usage metrics, semi-structured interviews, focus groups and observation in the field. Action research journals documented the overall process to achieve post-positivist recoverability rather than positivistic replicability. Analysis of the results from both field studies was iteratively synthesised to develop the Softbridge framework and consider its implications. The most significant finding is that awareness of social issues helps explain why users might not accept a technically sound communication system. It was found that when facilitated effectively by intermediaries, the Softbridge framework enables unintended uses of experimental artefacts that empower users to appropriate communication technologies on their own. Thus, the Softbridge framework helps to align technical and socio-cultural factors.

No description available.

As the number of spacecraft in simultaneous operation continues to grow, there is an increased dependency on ground-based navigation support. The current baseline system for deep space navigation utilizes Earth-based radiometric tracking, which requires long duration, often global, observations to perform orbit determination and generate a state update. The age, complexity, and high utilization of the assets that make up the Deep Space Network (DSN) pose a risk to spacecraft navigation performance. With increasingly complex mission operations, such as automated asteroid rendezvous or pinpoint planetary landing, the need for high accuracy and autonomous navigation capability is further reinforced. The Network-Based Navigation (NNAV) method developed in this research takes advantage of the growing inter-spacecraft communication network infrastructure to allow for autonomous state measurement. By embedding navigation headers into the data packets transmitted between nodes in the communication network, it is possible to provide an additional source of navigation capability. Simulation results indicate that as NNAV is implemented across the deep space network, the state estimation capability continues to improve, providing an embedded navigation network. To analyze the capabilities of NNAV, an analysis and simulation framework is designed that integrates navigation and communication analysis. Model-Based Systems Engineering (MBSE) and Agent-Based Modeling (ABM) techniques are utilized to foster a modular, expandable, and robust framework. This research has developed the Space Navigation Analysis and Performance Evaluation (SNAPE) framework. This framework allows for design, analysis, and optimization of deep space navigation and communication architectures. SNAPE captures high-level performance requirements and bridges them to specific functional requirements of the analytical implementation. The SNAPE framework is implemented in a representative prototype environment using the Python language and verified using industry standard packages. The capability of SNAPE is validated through a series of example test cases. These analyses focus on the performance of specific state measurements to state estimation performance, and demonstrate the core analytic functionality of the framework. Specific cases analyze the effects of initial error and measurement uncertainty on state estimation performance. The timing and frequency of state measurements are also investigated to show the need for frequent state measurements to minimize navigation errors. The dependence of navigation accuracy on timing stability and accuracy is also demonstrated. These test cases capture the functionality of the tool as well as validate its performance. The SNAPE framework is utilized to capture and analyze NNAV, both conceptually and analytically. Multiple evaluation cases are presented that focus on the Mars Science Laboratory's (MSL) Martian transfer mission phase. These evaluation cases validate NNAV and provide concrete evidence of its operational capability for this particular application. Improvement to onboard state estimation performance and reduced reliance on Earth-based assets is demonstrated through simulation of the MSL spacecraft utilizing NNAV processes and embedded packets within a limited network containing DSN and MRO. From the demonstrated state estimation performance, NNAV is shown to be a capable and viable method of deep space navigation. Through its implementation as a state augmentation method, the concept integrates with traditional measurements and reduces the dependence on Earth-based updates. Future development of this concept focuses on a growing network of assets and spacecraft, which allows for improved operational flexibility and accuracy in spacecraft state estimation capability and a growing solar system-wide navigation network.

Bibliography: leaves 272-280. / xi, 280 leaves : col. ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Computer Science, 2000

Thesis (Ph.D.) -- University of Adelaide, Dept. of Computer Science, 2000. / Bibliography: leaves 272-280.

Thesis(M.S.)--Auburn University, 2005. / Abstract. Vita. Includes bibliographic references.

Thesis (M.S.)--Auburn University, 2008. / Abstract. Vita. Includes bibliographical references (p. 58-62).

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 113-133).

- / -