South African Computer Journal - Volume 2000, Issue 26, 2000
Volumes & issues
Volume 2000, Issue 26, 2000
Source: South African Computer Journal 2000, pp 163 –171 (2000)More Less
Presence in Collaborative Virtual Environments (CVEs) can be classified into personal presence and co-presence. Personal presence is having a feeling of "being there" in the CVE oneself. Co-presence is having a feeling that one is in the same place as the other participants, and that one is collaborating with real people. In this paper we describe an experiment to investigate the effects that small group collaboration and interaction has on personal presence and specially co-presence in a CVE. We hypothesise that collaboration and interaction enhances co-presence in a CVE. We found that there was a large difference in co-presence between two CVEs which produced different levels of collaboration and interaction. This supports our hypotheses that just having virtual representations of others is not sufficient to create a high sense of co-presence, and that one needs collaboration and interaction in order to enhance co-presence in a CVE. We also found that. We measured personal presence subjectively, using a questionnaire developed by Slater et al. We have developed a co-presence questionnaire which assesses the levels of co-presence subjectively. We have also developed a collaboration questionnaire which measures group collaboration subjectively, as well as the degree of enjoyment and comfort with others in the group.
Author J.A. TrimbleSource: South African Computer Journal 2000, pp 172 –180 (2000)More Less
The goal of this research is to provide knowledge acquisition approaches that will contribute to reducing the risk involved in software development. Structured knowledge acquisition techniques can increase the rate of obtaining and developing knowledge, and the reliability of the knowledge acquired. This project builds on knowledge acquisition research from the expert systems and project management sub-disciplines. Knowledge representation is examined as a component of the knowledge acquisition process. This paper is intended to provide background material and guidelines that will assist in structured interaction with stakeholders in the software development process.
Author A.P. EngelbrechtSource: South African Computer Journal 2000, pp 181 –189 (2000)More Less
The Taylor series expansion of continuous functions has shown - in many fields - to be an extremely powerful tool to study the characteristics of such functions. This paper illustrates the power of the Taylor series expansion of multilayer feedforward neural networks. the paper shows how these expansions can be used to investigate positions of decision boundaries, to develop active learning strategies and to perform architecture selection.
Source: South African Computer Journal 2000, pp 190 –195 (2000)More Less
This paper explores the concept of "literacy requirements" for the web and in doing so examines a number of different ideas about literacy. the concept of readability is one important component of effective literacy with regard to websites. the research reported on here applies several existing and newly derived measures of readability to a selection of websites. Subsequent analysis is used to draw conclusions about the validity and applicability of these measures to determining website readability. A number of literacy measures were found to be appropriate for determining the readability of web page content. Two specific measures are the most significant in relationship to actual reading and navigating through online content. Further research into web literacy is proposed.
Source: South African Computer Journal 2000, pp 196 –200 (2000)More Less
The development of cryptographic logics to analyze security protocols has provided one technique for ensuring the correctness of security protocols. However, it is commonly acknowledged that analysis using a modal logic such as GNY tends to be inaccessible and obscure for the uninitiated. In this paper we describe a graphical tree-based specification environment which can be used to easily construct GNY statements using contextualized pop-up menus. the interface which we describe helps to move logic-based analysis out of the world of academia and into the mainstream market.
Author C. MuellerSource: South African Computer Journal 2000, pp 201 –206 (2000)More Less
The purpose of this short paper is to give some insights as to how computed values can aid algorithm design. A simple algorithm of the finding average is expressed in terms computed values illustrating how one can express an algorithm in a paradigm independent form. This same problem is used to show how a refinement process enables an algorithm to be developed from a specification. the refinement process enables alternatives to be explored at each step of the design. By looking at the number of computed values and their dependencies provides some simple tools for analysing the choices, this enables decisions to be made as to which alternative to select. Some simple theory is developed for describing the computed values. the advantage of the theory is that it is based on commonly used mathematical notation and restricted form predicate logic. Hence anyone with some basic mathematical background is able to understand the semantics of the theory.
Source: South African Computer Journal 2000, pp 207 –211 (2000)More Less
In this paper we describe the design and implementation of a system for representing context-free grammars in C++ . the system allows for grammar representation at the object level, providing enhanced modularity and flexibility when compared to traditional generator-based approaches. We also describe the transformation of grammar flow analysis problems into an object-oriented framework using the Visitor pattern, as well as the implementation of a top-down LL(1) parser. As such, this work represents the synthesis of three presently disparate fields in parser design and implementation: combinator parsing, fixpoint-based grammar flow analysis, and object-oriented design.
Conflict analysis as a means of enforcing static separation of duty requirements in workflow environmentsSource: South African Computer Journal 2000, pp 212 –216 (2000)More Less
The increasing reliance on information technology to support business processes has emphasised the need for information security mechanisms. This, however, has resulted in an ever-increasing workload in terms of security administration. Policy-based approaches have been proposed, promising to lighten the workload of security administrators. Separation of duty is one of the principles cited as a requirement when setting up these policy-based mechanisms. Different types of separation of duty policies exist. They can be categorised into policies that can be enforced at administration time, viz. static separation of duty requirements and policies that can be enforced only at execution time, viz. dynamic separation of duty requirements. This paper deals with specifying static separation of duty requirements in role-based workflow environments. It proposes a mathematical model based on the concept of "Sconflicting entities"T to express static separation of duty requirements. It provides a detailed explanation of the integrity checking that must take place at administration time to ensure that specified separation of duty requirements are honoured.
Author P. KotzeSource: South African Computer Journal 2000, pp 217 –221 (2000)More Less
Graph theory is an established field of study. the concepts of graphs and transition networks are well-known in computing. Mathematical expressions of some kind are almost always used to define graphs. Although these definitions are generally considered to be exact, one runs into difficulty when attempting to specify various graph definitions using a model-based specification notation such as Z, or when implementation structures are considered. In order to successfully do so one has to change the general mathematical definitions of graphs. This paper provides a set of such alternative definitions based on the use of bag structures.
Source: South African Computer Journal 2000, pp 222 –227 (2000)More Less
Current research to develop artificial human vision relies on the inducing of digital image-like effects in the brain. This paper reviews related projects underway internationally, and then discusses aspects of image processing which could provide enhanced visual information to users of such systems, where image quality is severely restricted. Some more advanced options involving computed pseudo-scenes providing virtual understanding of natural visual scenes are proposed.
Source: South African Computer Journal 2000, pp 228 –231 (2000)More Less
A computer-based training (CBT) system was used to teach Computer Literacy to full-time students at the University of the Western Cape. This approach was successful in creating computer literate students as well as creating an opportunity for students from educationally disadvantaged schools to enter the Computer Science course. the students experienced this new approach to learning positively. This has laid the foundation to export the computer-based education model to communities outside the university. Lifelong learning opportunities will thus be created.
Source: South African Computer Journal 2000, pp 231 –236 (2000)More Less
Tertiary institutions in South Africa are faced with dealing with diversity in all its forms in our classrooms. Information Systems, Information Technology and Computer Science students need to learn to work with people who are different from themselves in order to learn to work effectively in the work environment to which they will go. Teaching students in a multicultural classroom to be able to practise their professionin multicultural settings is crucial. This paper looks at the problems that occur if we ignore diversity, some techniques for dealing with diversity, especially when using group work and then presents results of a series of four case studies where some of these techniques were applied.
Source: South African Computer Journal 2000, pp 237 –242 (2000)More Less
As a result of the popularity of graphical user interfaces, it is now almost impossible to buy a programming language compiler - instead, one purchases a development environment. Of course, we can scoff at the distinction and say that a development environment is nothing more than a programming language with visual (as opposed to syntactic) sugar. We believe, however, that this view must change if safer and more responsible programming languages are to be created for the next generation of programmer. Within this paper, we will argue that a more theoretical approach should be taken to the development of programming environments and suggest ways in which this may be achieved.
Source: South African Computer Journal 2000, pp 242 –246 (2000)More Less
Technology influences education in a number of ways. One of these influences is in the classroom, creating what can be called a computer supported learning environment. A computer supported learning environment has many tools available for the enhancing of the learning experience. Some of these tools are educational resources tempered with technology. These resources include interactive tutorials, animations and simulations. It is important for an educator to store these resources in such a way as to make them accessible to both students and fellow educators. In storing the resources, there are several factors that have to be remembered. These factors include the reusability of materials, the linking of materials to courses and the navigation through the course sites.
Source: South African Computer Journal 2000, pp 247 –251 (2000)More Less
Presence has become a key concept in characterizing and evaluating Virtual Environments. Our contribution is to show that current measures of Presence, as a metric of users' experience of Virtual Environments, are highly problematic: results from the literature cannot be repeated and it lacks a theoretical basis. We synthesize results from three experiments we conducted and in conclusion point the way to alternative approaches to the problem of characterizing Collaborative Virtual Environments.
Source: South African Computer Journal 2000, pp 252 –255 (2000)More Less
Virtual Multicasting (VMC) is a specific instance of a more general idea, Information Mass Transit (IMT). IMT aims to reduce the waste of bandwidth resulting from individual streams of data, while improving user-level latency. By analogy with mass transit where shared transport reduces the load on infrastructure, IMT aims to use networks and other infrastructure more efficiently. VMC combines some of the benefits of caching (transparency, dynamic adaptation to workload) and multicast (reducing duplicated traffic).