Research Publications

Extensive research has been done using machine learning techniques for hand gesture recognition (HGR) using camera-based devices; such as the Leap Motion Controller (LMC). However, limited research has investigated machine learning techniques for HGR in virtual reality applications (VR). This paper reports on the design, implementation, and evaluation of a static HGR system for VR applications using the LMC. The gesture recognition system incorporated a lightweight feature vector of five normalized tip-to-palm distances and a k-nearest neighbour (kNN) classifier. The system was evaluated in terms of response time, accuracy and usability using a case-study VR stellar data visualization application created in the Unreal Engine 4. An average gesture classification time of 0.057ms with an accuracy of 82.5% was achieved on four distinct gestures, which is comparable with previous results from Sign Language recognition systems. This shows the potential of HGR machine learning techniques applied to VR, which were previously applied to non-VR scenarios such as Sign Language recognition.

@{156,
  author = {A. Clark and Deshen Moodley},
  title = {A System for a Hand Gesture-Manipulated Virtual Reality Environment},
  abstract = {Extensive research has been done using machine learning techniques for hand gesture recognition (HGR) using camera-based devices; such as the Leap Motion Controller (LMC). However, limited research has investigated machine learning techniques for HGR in virtual reality applications (VR). This paper reports on the design, implementation, and evaluation of a static HGR system for VR applications using the LMC. The gesture recognition system incorporated a lightweight feature vector of five normalized tip-to-palm distances and a k-nearest neighbour (kNN) classifier. The system was evaluated in terms of response time, accuracy and usability using a case-study VR stellar data visualization application created in the Unreal Engine 4. An average gesture classification time of 0.057ms with an accuracy of 82.5% was achieved on four distinct gestures, which is comparable with previous results from Sign Language recognition systems. This shows the potential of HGR machine learning techniques applied to VR, which were previously applied to non-VR scenarios such as Sign Language recognition.},
  year = {2016},
  journal = {Annual Conference of the South African Institute of Computer Scientists and Information Technologists (SAICSIT 2016)},
  pages = {10},
  month = {26/09-28/09},
  publisher = {ACM},
  address = {Johannesburg},
  isbn = {978-1-4503-4805-8},
  doi = {http://dx.doi.org/10.1145/2987491.2987511},
}

We investigate the impact of recent advances in speech recognition techniques for under-resourced languages. Specifically, we review earlier results published on the Lwazi ASR corpus of South African languages, and experiment with additional acoustic modeling approaches. We demonstrate large gains by applying current state-of-the-art techniques, even if the data itself is neither extended nor improved. We analyze the various performance improvements observed, report on comparative performance per technique – across all eleven languages in the corpus – and discuss the implications of our findings for under-resourced languages in general.

@{153,
  author = {Charl Van Heerden and Neil Kleynhans and Marelie Davel},
  title = {Improving the Lwazi ASR baseline},
  abstract = {We investigate the impact of recent advances in speech recognition techniques for under-resourced languages. Specifically, we review earlier results published on the Lwazi ASR corpus of South African languages, and experiment with additional acoustic modeling approaches. We demonstrate large gains by applying current state-of-the-art techniques, even if the data itself is neither extended nor improved. We analyze the various performance improvements observed, report on comparative performance per technique – across all eleven languages in the corpus – and discuss the implications of our findings for under-resourced languages in general.},
  year = {2016},
  journal = {Interspeech},
  pages = {3529-3538},
  month = {08/09-12/09},
  address = {San Francisco, USA},
  doi = {http://dx.doi.org/10.21437/Interspeech.2016-1412},
}

No Abstract

@misc{150,
  author = {James Lapalme and Aurona Gerber and Alta van der Merwe and John Zachman and Marne de Vries and Knut Hinkelmann},
  title = {Exploring the future of enterprise architecture: A Zachman perspective.},
  abstract = {No Abstract},
  year = {2016},
  url = {http://www.sciencedirect.com/science/journal/01663615/79},
}

No Abstract

@misc{149,
  author = {Henriette Harmse and Katarina Britz and Aurona Gerber},
  title = {Armstrong Relations for Ontology Design and Evaluation},
  abstract = {No Abstract},
  year = {2016},
  url = {http://ceur-ws.org/Vol-1577/},
}

No Abstract

@article{148,
  author = {Knut Hinkelmann and Aurona Gerber and Dimitris Karagiannis and Barbara Thoenssen and Alta van der Merwe and Robert Woitsch},
  title = {A new paradigm for the continuous alignment of business and IT: Combining enterprise architecture modelling and enterprise ontology},
  abstract = {No Abstract},
  year = {2016},
  journal = {Computers in Industry},
  volume = {79},
  publisher = {Sciencedirect},
  url = {http://www.sciencedirect.com/science/article/pii/S0166361515300270},
}

No Abstract

@misc{146,
  author = {Brink van der Merwe},
  title = {The Output Size Problem for String-to-Tree Transducers},
  abstract = {No Abstract},
  year = {2016},
  url = {http://www.ims.uni-stuttgart.de/events/TTATT2016},
}

No Abstract

@{145,
  author = {Brink van der Merwe},
  title = {Analyzing Matching Time Behavior of Backtracking Regular Expression Matchers by Using Ambiguity of NFA.},
  abstract = {No Abstract},
  year = {2016},
  journal = {21st International Conference on Implementation and Application of Automata},
  pages = {322-334},
  month = {19/07-22/07},
}

We propose a method for an agent to revise its incomplete probabilistic beliefs when a new piece of propositional information is observed. In this work, an agent’s beliefs are represented by a set of probabilistic formulae – a belief base. The method involves determining a representative set of ‘boundary’ probability distributions consistent with the current belief base, revising each of these probability distributions and then translating the revised information into a new belief base. We use a version of Lewis Imaging as the revision operation. The correctness of the approach is proved. An analysis of the approach is done against six rationality postulates. The expressivity of the belief bases under consideration are rather restricted, but has some applications. We also discuss methods of belief base revision employing the notion of optimum entropy, and point out some of the benefits and difficulties in those methods. Both the boundary distribution method and the optimum entropy method are reasonable, yet yield different results.

@{144,
  author = {Gavin Rens and Tommie Meyer and Giovanni Casini},
  title = {On Revision of Partially Specified Convex Probabilistic Belief Bases},
  abstract = {We propose a method for an agent to revise its incomplete probabilistic beliefs when a new piece of propositional information is observed. In this work, an agent’s beliefs are represented by a set of probabilistic formulae – a belief base. The method involves determining a representative set of ‘boundary’ probability distributions consistent with the current belief base, revising each of these probability distributions and then translating the revised information into a new belief base. We use a version of Lewis Imaging as the revision operation. The correctness of the approach is proved. An analysis of the approach is done against six rationality postulates. The expressivity of the belief bases under consideration are rather restricted, but has some applications. We also discuss methods of belief base revision employing the notion of optimum entropy, and point out some of the benefits and difficulties in those methods. Both the boundary distribution method and the optimum entropy method are reasonable, yet yield different results.},
  year = {2016},
  journal = {European Conference on Artificial Intelligence (ECAI)},
  pages = {921-929},
  month = {31/08-02/09},
}

No Abstract

@{143,
  author = {Steve Kroon and PB Le Roux and Willem Bester},
  title = {DSaaS:  A cloud Service for Persistent Data Structures},
  abstract = {No Abstract},
  year = {2016},
  journal = {CLOSER, 6th International Conference on Cloud Computing and Services Science},
  pages = {37-48},
  month = {23/04-25/04},
  address = {Portugal},
  isbn = {978-989-758-182-3},
}

Convolutional neural networks have shown great promise in both general image segmentation problems as well as bioimage segmentation. In this paper, the application of different convolutional network architectures is explored on the C. elegans live/dead assay dataset from the Broad Bioimage Benchmark Collection. These architectures include a standard convolutional network which produces single pixel outputs, as well as Fully Convolutional Networks (FCN) for patch prediction. It was shown that the custom image processing pipeline, which achieved a worm segmentation accuracy of 94%, was outperformed by all of the architectures considered, with the best being 97.3% achieved by a FCN with a single downsampling layer. These results demonstrate the promise of employing convolutional neural network architectures as an alternative to ad-hoc image processing pipelines on optical microscopy images of C. elegans.

@{142,
  author = {Hennie de Villiers and Stiaan Wiehman},
  title = {Semantic Segmentation of Bioimages Using Convolutional Neural Networks},
  abstract = {Convolutional neural networks have shown great promise in both general image segmentation problems as well as bioimage segmentation. In this paper, the application of different convolutional network architectures is explored on the C. elegans live/dead assay dataset from the Broad Bioimage Benchmark Collection. These architectures include a standard convolutional network which produces single pixel outputs, as well as Fully Convolutional Networks (FCN) for patch prediction. It was shown that the custom image processing pipeline, which achieved a worm segmentation accuracy of 94%, was outperformed by all of the architectures considered, with the best being 97.3% achieved by a FCN with a single downsampling layer. These results demonstrate the promise of employing convolutional neural network architectures as an alternative to ad-hoc image processing pipelines on optical microscopy images of C. elegans.},
  year = {2016},
  journal = {2016 International Joint Conference on Neural Networks (IJCNN)},
  pages = {624-631},
  month = {24/07-29/07},
  address = {Singapore},
  isbn = {978-1-5090-0620-5},
}

No Abstract

@{141,
  author = {G.J. Greene and Bernd Fischer},
  title = {CVExplorer: Identifying Candidate Developers by Mining and Exploring Their Open Source Contributions},
  abstract = {No Abstract},
  year = {2016},
  journal = {Automated Software Engineering},
  pages = {804-809},
  month = {03/09-07/09},
  isbn = {978-1-4503-3845-5},
}

A framework for an agent to change its probabilistic beliefs after a stream of noisy observations is received is proposed. Observations which are no longer relevant, become default assumptions until overridden by newer, more prevalent observations. A distinction is made between background and foreground beliefs. Agent actions and environment events are distinguishable and form part of the agent model. It is left up to the agent designer to provide an environment model; a submodel of the agent model. An example of an environment model is provided in the paper, and an example scenario is based on it. Given the particular form of the agent model, several ‘patterns of cognition’ can be identified. An argument is made for four particular patterns.

@misc{140,
  author = {Gavin Rens},
  title = {A Stochastic Belief Change Framework with an Observation Stream and Defaults as Expired Observations},
  abstract = {A framework for an agent to change its probabilistic beliefs after a stream of noisy observations is received is proposed. Observations which are no longer relevant, become default assumptions until overridden by newer, more prevalent observations. A distinction is made between background and foreground beliefs. Agent actions and environment events are distinguishable and form part of the agent model. It is left up to the agent designer to provide an environment model; a submodel of the agent model. An example of an environment model is provided in the paper, and an example scenario is based on it. Given the particular form of the agent model, several ‘patterns of cognition’ can be identified. An argument is made for four particular patterns.},
  year = {2016},
}

Sometimes, strictly choosing between belief revision and belief update is inadequate in a dynamical, uncertain environment. Boutilier combined the two notions to allow updates in response to external changes to inform an agent about its prior beliefs. His approach is based on ranking functions. Rens proposed a new method to trade off probabilistic revision and update, in proportion to the agent’s confidence for whether to revise or update. In this paper, we translate Rens’s approach from a probabilistic setting to a setting with ranking functions. Given the translation, we are able to compare Boutilier’s and Rens’s approaches.We found that Rens’s approach is an extension of Boutilier’s.

@misc{139,
  author = {Gavin Rens and Gabriele Kern-Isberner},
  title = {An Approach to Qualitative Belief Change Modulo Ontic Strength},
  abstract = {Sometimes, strictly choosing between belief revision and belief update is inadequate in a dynamical, uncertain environment. Boutilier combined the two notions to allow updates in response to external changes to inform an agent about its prior beliefs. His approach is based on ranking functions. Rens proposed a new method to trade off probabilistic revision and update, in proportion to the agent’s confidence for whether to revise or update. In this paper, we translate Rens’s approach from a probabilistic setting to a setting with ranking functions. Given the translation, we are able to compare Boutilier’s and Rens’s approaches.We found that Rens’s approach is an extension of Boutilier’s.},
  year = {2016},
}

No Abstract

@misc{138,
  author = {G.J. Greene and Bernd Fischer},
  title = {Single-Focus Broadening Navigation in Concept Lattices},
  abstract = {No Abstract},
  year = {2016},
  url = {https://cla2016.hse.ru/data/2016/07/24/1119022942/CDUD2016.pdf#page=39},
}

We venture beyond the customary semantic approach in NMR, namely that of placing orderings on worlds (or valuations). In a modal-logic setting, we motivate and investigate the idea of ordering elements of the accessibility relations in Kripke frames, i.e, world pairs (w,w') (or arrows). The underlying intuition is that some world pairs may be seen as more normal (or typical, or expected) than others. We show this delivers an elegant and intuitive semantic construction, which gives a new perspective on present notions of defeasible necessity. From a modeler's perspective, the new framework we propose is more intuitively appealing. Technically, though, the revisited logic happens to not substantively increase the expressive power of the previously defined preferential modalities. This conclusion follows from an analysis of both semantic constructions via a generalisation of bisimulations to the preferential case. Lest this be seen as a negative result, it essentially means that reasoners based on the previous semantics (which have been shown to preserve the computational complexity of the underlying classical modal language) suffice for reasoning over the new semantics. Finally, we show that the kind of construction we here propose has many fruitful applications, notably in a description-logic context, where it provides the foundations on which to ground useful notions of defeasibility in ontologies yet to be explored.

@misc{135,
  author = {Katarina Britz and Ivan Varzinczak},
  title = {Preferential modalities revisited},
  abstract = {We venture beyond the customary semantic approach in NMR, namely that of placing orderings on worlds (or valuations). In a modal-logic setting, we motivate and investigate the idea of ordering elements of the accessibility relations in Kripke frames, i.e, world pairs (w,w') (or arrows). The underlying intuition is that some world pairs may be seen as more normal (or typical, or expected) than others. We show this delivers an elegant and intuitive semantic construction, which gives a new perspective on present notions of defeasible necessity. From a modeler's perspective, the new framework we propose is more intuitively appealing. Technically, though, the revisited logic happens to not substantively increase the expressive power of the previously defined preferential modalities. This conclusion follows from an analysis of both semantic constructions via a generalisation of bisimulations to the preferential case. Lest this be seen as a negative result, it essentially means that reasoners based on the previous semantics (which have been shown to preserve the computational complexity of the underlying classical modal language) suffice for reasoning over the new semantics. Finally, we show that the kind of construction we here propose has many fruitful applications, notably in a description-logic context, where it provides the foundations on which to ground useful notions of defeasibility in ontologies yet to be explored.},
  year = {2016},
  url = {http://nmr2016.cs.uct.ac.za/proceedings_nmr2016_online.pdf},
}

I propose a framework for an agent to change its probabilistic beliefs when a new piece of propositional information alpha is observed. Traditionally, belief change occurs by either a revision process or by an update process, depending on whether the agent is informed with alpha in a static world or, respectively, whether alpha is a ‘signal’ from the environment due to an event occurring. Boutilier suggested a unified model of qualitative belief change, which “combines aspects of revision and update, providing a more realistic characterization of belief change.” In this paper, I propose a unified model of quantitative belief change, where an agent’s beliefs are represented as a probability distribution over possible worlds. As does Boutilier, I take a dynamical systems perspective. The proposed approach is evaluated against several rationality postulated, and some properties of the approach are worked out.

@misc{132,
  author = {Gavin Rens},
  title = {On Stochastic Belief Revision and Update and their Combination},
  abstract = {I propose a framework for an agent to change its probabilistic beliefs when a new piece of propositional information alpha is observed. Traditionally, belief change occurs by either a revision process or by an update process, depending on whether the agent is informed with alpha in a static world or, respectively, whether alpha is a ‘signal’ from the environment due to an event occurring. Boutilier suggested a unified model of qualitative belief change, which “combines aspects of revision and update, providing a more realistic characterization of belief change.” In this paper, I propose a unified model of quantitative belief change, where an agent’s beliefs are represented as a probability distribution over possible worlds. As does Boutilier, I take a dynamical systems perspective. The proposed approach is evaluated against several rationality postulated, and some properties of the approach are worked out.},
  year = {2016},
  isbn = {ISSN 0933-6192},
}

We propose a method for an agent to revise its incomplete probabilistic beliefs when a new piece of propositional information is observed. In this work, an agent’s beliefs are represented by a set of probabilistic formulae – a belief base. The method involves determining a representative set of ‘boundary’ probability distributions consistent with the current belief base, revising each of these probability distributions and then translating the revised information into a new belief base. We use a version of Lewis Imaging as the revision operation. The correctness of the approach is proved. The expressivity of the belief bases under consideration are rather restricted, but has some applications. We also discuss methods of belief base revision employing the notion of optimum entropy, and point out some of the benefits and difficulties in those methods. Both the boundary distribution method and the optimum entropy method are reasonable, yet yield different results.

@misc{131,
  author = {Gavin Rens and Tommie Meyer and Giovanni Casini},
  title = {Revising Incompletely Specified Convex Probabilistic Belief Bases},
  abstract = {We propose a method for an agent to revise its incomplete probabilistic beliefs when a new piece of propositional information is observed. In this work, an agent’s beliefs are represented by a set of probabilistic formulae – a belief base. The method involves determining a representative set of ‘boundary’ probability distributions consistent with the current belief base, revising each of these probability distributions and then translating the revised information into a new belief base. We use a version of Lewis Imaging as the revision operation. The correctness of the approach is proved. The expressivity of the belief bases under consideration are rather restricted, but has some applications. We also discuss methods of belief base revision employing the notion of optimum entropy, and point out some of the benefits and difficulties in those methods. Both the boundary distribution method and the optimum entropy method are reasonable, yet yield different results.},
  year = {2016},
  isbn = {ISSN 0933-6192},
}

@{582,
  author = {Joey van Vuuren and Louise Leenen and Marthie Grobler and K.F. Chan and Z. Khan},
  title = {Modelling the Cybersecurity Environment Using Morphological Ontology Design Engineering},
  abstract = {},
  year = {2015},
  journal = {Proceedings of the 10th International Conference on Cyber Warfare and Security (ICCWS 2015)},
  month = {March 2015},
  publisher = {Academic Conferences International},
  address = {Kruger National Park, South Africa},
}

@{581,
  author = {Michael Aschmann and Joey van Vuuren and Louise Leenen},
  title = {Cyber Armies: The Unseen Military in the Grid},
  abstract = {},
  year = {2015},
  journal = {Proceedings of the 10th International Conference on Cyber Warfare and Security (ICCWS 2015)},
  month = {March 2015},
  publisher = {Academic Conferences International},
  address = {Kruger National Park, South Africa},
}

@{580,
  author = {Louise Leenen and Tommie Meyer},
  title = {The Use of Semantic Technologies in Cyber Defence},
  abstract = {},
  year = {2015},
  journal = {Proceedings of the 10th International Conference on Cyber Warfare and Security (ICIW 2015)},
  month = {March 2015},
  publisher = {Academic Conferences International},
  address = {Kruger National Park, South Africa},
}

@{579,
  author = {Peter Chan and Jacques Theron and Renier van Heerden and Louise Leenen},
  title = {An Ontological Knowledge Base for Cyber Network Attack Planning},
  abstract = {},
  year = {2015},
  journal = {Proceedings of the 10th International Conference on Cyber Warfare and Security (ICIW 2015)},
  month = {March 2015},
  publisher = {Academic Conferences International},
  address = {Kruger National Park, South Africa},
}

Cybersecurity has become a critical element of the national security of countries. A cyber-army is a group of soldiers highly skilled in information technology with cyber skills. Cyber-armies are the unseen military cyber power which countries should employ to maintain national cybersecurity. A cyber-army has the ability to launch cyberattacks and collect information in order to gain a strategic military advantage. In this paper, selected cyber-armies are compared. The focus is on the establishment of an African Cyber-Army to defend and protect cyber sovereignty. An African Cyber-Army has to serve nations whose citizens often have low levels of cybersecurity awareness in conjunction with rapidly growing rates of access to cyberspace.

@article{570,
  author = {Michael Aschmann and Joey van Vuuren and Louise Leenen},
  title = {Towards the Establishment of an African Cyber-Army},
  abstract = {Cybersecurity has become a critical element of the national security of countries. A cyber-army is a group of soldiers highly skilled in information technology with cyber skills. Cyber-armies are the unseen military cyber power which countries should employ to maintain national cybersecurity. A cyber-army has the ability to launch cyberattacks and collect information in order to gain a strategic military advantage. In this paper, selected cyber-armies are compared. The focus is on the establishment of an African Cyber-Army to defend and protect cyber sovereignty. An African Cyber-Army has to serve nations whose citizens often have low levels of cybersecurity awareness in conjunction with rapidly growing rates of access to cyberspace.},
  year = {2015},
  journal = {Journal of Information Warfare},
  volume = {14},
  issue = {3},
  publisher = {ArmisteadTEC},
}