Research Publications

2021

1.
Gerber A, Eybers S. Converting to Inclusive Online Flipped Classrooms in Response to Covid-19 Lockdown. South African Journal of Higher Education. 2021;35(4). doi:10.20853/35-4-4285.

The global Covid-19 pandemic caused havoc in higher education teaching routines and several residential institutions encouraged instructors to convert existing modules to flipped classrooms as part of an online, blended learning strategy. Even though this seems a reasonable request, instructors straightaway encountered challenges which include a vague concept of what an online flipped classroom entails within a higher education context, a lack of guidelines for converting an existing module, facilitating learner engagement as well as unique challenges for inclusion of all learners in a digitally divided developing country in Covid-19 lockdown. In order to respond, we embarked on a study to identify the distinguishing characteristics of flipped classrooms to understand the as-is and to-be scenarios using a systematic literature review. The characteristics were used to develop of design considerations to convert to an online flipped classroom for higher education taking our diverse learner profiles into account. We subsequently converted a short module in an information systems department and shortly report on our experience.

@article{436,
  author = {Aurona Gerber and Sunet Eybers},
  title = {Converting to Inclusive Online Flipped Classrooms in Response to Covid-19 Lockdown},
  abstract = {The global Covid-19 pandemic caused havoc in higher education teaching routines and several residential institutions encouraged instructors to convert existing modules to flipped classrooms as part of an online, blended learning strategy. Even though this seems a reasonable request, instructors straightaway encountered challenges which include a vague concept of what an online flipped classroom entails within a higher education context, a lack of guidelines for converting an existing module, facilitating learner engagement as well as unique challenges for inclusion of all learners in a digitally divided developing country in Covid-19 lockdown. In order to respond, we embarked on a study to identify the distinguishing characteristics of flipped classrooms to understand the as-is and to-be scenarios using a systematic literature review. The characteristics were used to develop of design considerations to convert to an online flipped classroom for higher education taking our diverse learner profiles into account. We subsequently converted a short module in an information systems department and shortly report on our experience.},
  year = {2021},
  journal = {South African Journal of Higher Education},
  volume = {35},
  pages = {34-57},
  issue = {4},
  isbn = {1753-5913},
  url = {https://journals.co.za/doi/10.20853/35-4-4285},
  doi = {10.20853/35-4-4285},
}
1.
Luzipo S, Gerber A. A Systematic Literature Review of Blockchain Consensus Protocols. Lecture Notes in Computer Science. 2021;12896. doi:10.1007/978-3-030-85447-8_48.

Blockchain is the underlying technology behind Bitcoin, the first digital currency, and due to the rapid growth of Bitcoin, there is significant interest in blockchain as the enabler of digital currencies due to the consensus distributed ledger model. The rise and the success of alternative cryptocurrencies such as Ethereum and Ripple has supported the development of blockchain technology, but the performance of blockchain applications has been documented as a significant obstacle for adoption. At the core of blockchain is a consensus protocol, which plays a key role in maintaining the safety, performance and efficiency of the blockchain network. Several consensus protocols exist, and the use of the right consensus protocol is crucial to ensure adequate performance of any blockchain application. However, there is a lack of documented overview studies even though there is agreement in the literature about the importance and understanding of blockchain consensus protocols. In this study, we adopt a systematic literature review (SLR) to investigate the current status of consensus protocols used for blockchain together with the identified limitations of these protocols. The results of this study include an overview of different consensus protocols as well as consensus protocol limitations and will be of value for any practitioner or scholar that is interested in blockchain applications.

@article{435,
  author = {Sikho Luzipo and Aurona Gerber},
  title = {A Systematic Literature Review of Blockchain Consensus Protocols},
  abstract = {Blockchain is the underlying technology behind Bitcoin, the first digital currency, and due to the rapid growth of Bitcoin, there is significant interest in blockchain as the enabler of digital currencies due to the consensus distributed ledger model. The rise and the success of alternative cryptocurrencies such as Ethereum and Ripple has supported the development of blockchain technology, but the performance of blockchain applications has been documented as a significant obstacle for adoption. At the core of blockchain is a consensus protocol, which plays a key role in maintaining the safety, performance and efficiency of the blockchain network. Several consensus protocols exist, and the use of the right consensus protocol is crucial to ensure adequate performance of any blockchain application. However, there is a lack of documented overview studies even though there is agreement in the literature about the importance and understanding of blockchain consensus protocols. In this study, we adopt a systematic literature review (SLR) to investigate the current status of consensus protocols used for blockchain together with the identified limitations of these protocols. The results of this study include an overview of different consensus protocols as well as consensus protocol limitations and will be of value for any practitioner or scholar that is interested in blockchain applications.},
  year = {2021},
  journal = {Lecture Notes in Computer Science},
  volume = {12896},
  pages = {580-595},
  publisher = {Springer},
  address = {Cham},
  isbn = {978-3-030-85447-8},
  url = {https://link.springer.com/chapter/10.1007/978-3-030-85447-8_48},
  doi = {10.1007/978-3-030-85447-8_48},
}
1.
Casini G, Meyer T, Varzinczak I. Contextual Conditional Reasoning. In: 35th AAAI Conference on Artificial Intelligence. Online: AAAI Press; 2021.

We extend the expressivity of classical conditional reasoning by introducing context as a new parameter. The enriched conditional logic generalises the defeasible conditional setting in the style of Kraus, Lehmann, and Magidor, and allows for a refined semantics that is able to distinguish, for example, between expectations and counterfactuals. In this paper we introduce the language for the enriched logic and define an appropriate semantic framework for it. We analyse which properties generally associated with conditional reasoning are still satisfied by the new semantic framework, provide a suitable representation result, and define an entailment relation based on Lehmann and Magidor’s generally-accepted notion of Rational Closure.

@{430,
  author = {Giovanni Casini and Tommie Meyer and Ivan Varzinczak},
  title = {Contextual Conditional Reasoning},
  abstract = {We extend the expressivity of classical conditional reasoning by introducing context as a new parameter. The enriched
conditional logic generalises the defeasible conditional setting in the style of Kraus, Lehmann, and Magidor, and allows for a refined semantics that is able to distinguish, for example, between expectations and counterfactuals. In this paper we introduce the language for the enriched logic and define an appropriate semantic framework for it. We analyse which properties generally associated with conditional reasoning are still satisfied by the new semantic framework, provide a suitable representation result, and define an entailment relation based on Lehmann and Magidor’s generally-accepted notion of Rational Closure.},
  year = {2021},
  journal = {35th AAAI Conference on Artificial Intelligence},
  pages = {6254-6261},
  month = {02/02/2021-09/02/2021},
  publisher = {AAAI Press},
  address = {Online},
}
1.
Casini G, Meyer T, Paterson-Jones G. KLM-Style Defeasibility for Restricted First-Order Logic. In: 19th International Workshop on Non-Monotonic Reasoning. Online; 2021. https://drive.google.com/open?id=1WSIl3TOrXBhaWhckWN4NLXoD9AVFKp5R.

We extend the KLM approach to defeasible reasoning to be applicable to a restricted version of first-order logic. We describe defeasibility for this logic using a set of rationality postulates, provide an appropriate semantics for it, and present a representation result that characterises the semantic description of defeasibility in terms of the rationality postulates. Based on this theoretical core, we then propose a version of defeasible entailment that is inspired by Rational Closure as it is defined for defeasible propositional logic and defeasible description logics. We show that this form of defeasible entailment is rational in the sense that it adheres to our rationality postulates. The work in this paper is the first step towards our ultimate goal of introducing KLM-style defeasible reasoning into the family of Datalog+/- ontology languages.

@{429,
  author = {Giovanni Casini and Tommie Meyer and Guy Paterson-Jones},
  title = {KLM-Style Defeasibility for Restricted First-Order Logic},
  abstract = {We extend the KLM approach to defeasible reasoning to be applicable to a restricted version of first-order logic. We describe defeasibility for this logic using a set of rationality postulates, provide an appropriate semantics for it, and present a representation result that characterises the semantic description of defeasibility in terms of the rationality postulates. Based on this theoretical core, we then propose a version of defeasible entailment that is inspired by Rational Closure as it is defined for defeasible propositional logic and defeasible description logics. We show that this form of defeasible entailment is rational in the sense that it adheres to our rationality postulates. The work in this paper is the first step towards our ultimate goal of introducing KLM-style defeasible reasoning into the family of Datalog+/- ontology languages.},
  year = {2021},
  journal = {19th International Workshop on Non-Monotonic Reasoning},
  pages = {184-193},
  month = {03/11/2021-05/11/2021},
  address = {Online},
  url = {https://drive.google.com/open?id=1WSIl3TOrXBhaWhckWN4NLXoD9AVFKp5R},
}
1.
Wanyana T, Moodley D. An Agent Architecture for Knowledge Discovery and Evolution. In: KI 2021: Advances in Artificial Intelligence. volume 12873. Cham: Springer International Publishing; 2021. doi:https://doi.org/10.1007/978-3-030-87626-5_18.

The abductive theory of method (ATOM) was recently proposed to describe the process that scientists use for knowledge discovery. In this paper we propose an agent architecture for knowledge discovery and evolution (KDE) based on ATOM. The agent incorporates a combination of ontologies, rules and Bayesian networks for representing different aspects of its internal knowledge. The agent uses an external AI service to detect unexpected situations from incoming observations. It then uses rules to analyse the current situation and a Bayesian network for finding plausible explanations for unexpected situations. The architecture is evaluated and analysed on a use case application for monitoring daily household electricity consumption patterns.

@inbook{425,
  author = {Tezira Wanyana and Deshen Moodley},
  title = {An Agent Architecture for Knowledge Discovery and Evolution},
  abstract = {The abductive theory of method (ATOM) was recently proposed to describe the process that scientists use for knowledge discovery. In this paper we propose an agent architecture for knowledge discovery and evolution (KDE) based on ATOM. The agent incorporates a combination of ontologies, rules and Bayesian networks for representing different aspects of its internal knowledge. The agent uses an external AI service to detect unexpected situations from incoming observations. It then uses rules to analyse the current situation and a Bayesian network for finding plausible explanations for unexpected situations. The architecture is evaluated and analysed on a use case application for monitoring daily household electricity consumption patterns.},
  year = {2021},
  journal = {KI 2021: Advances in Artificial Intelligence},
  edition = {volume 12873},
  pages = {241-256},
  publisher = {Springer International Publishing},
  address = {Cham},
  isbn = {978-3-030-87626-5},
  doi = {https://doi.org/10.1007/978-3-030-87626-5_18},
}
1.
Mbonye V, Price CS. Students’ use of on-campus wireless networks: Analysis by residence type. In: 2021 International Conference on Artificial Intelligence, Big Data, Computing and Data Communication Systems (icABCD). Durban, South Africa: IEEE; 2021. doi:https://doi.org/10.1109/icABCD51485.2021.9519327.

Universities supply free Wi-Fi to registered students on campus to access learning materials. Many issues could reduce the quality of students' Wi-Fi use, e.g., devices using different Wi-Fi standards than those used on campus, and numerous students accessing Wi-Fi through a single access point simultaneously. Understanding where, when and how students use Wi-Fi on campus can help IT administrators to provide an adequate Wi-Fi service. This pre-COVID study adopted a mixed method approach. Questionnaires were completed by a representative sample of 373 students on the Westville campus of the University of KwaZulu-Natal, South Africa. Two Information Communication Services (lCS) staff members were interviewed to gain insights into how the Wi-Fi was set up, and their perspectives on how students utilise the Wi-Fi. The questionnaire data were analysed statistically, and interview results were used to explain results. The students' most used venues, and the places they encountered poor and best Wi-Fi signal quality, are presented, along with the durations of use and problems encountered. When analysing these results by students' residence type, each category showed a different pattern of use. These results can help IT administrators understand where to improve the Wi-Fi quality, if necessary. It is particularly useful if some categories of students return to campus, while others do not, e.g. as COVID-19 lockdowns ease.

@{424,
  author = {V. Mbonye and C. Sue Price},
  title = {Students’ use of on-campus wireless networks: Analysis by residence type},
  abstract = {Universities supply free Wi-Fi to registered students on campus to access learning materials. Many issues could reduce the quality of students' Wi-Fi use, e.g., devices using different Wi-Fi standards than those used on campus, and numerous students accessing Wi-Fi through a single access point simultaneously. Understanding where, when and how students use Wi-Fi on campus can help IT administrators to provide an adequate Wi-Fi service. This pre-COVID study adopted a mixed method approach. Questionnaires were completed by a representative sample of 373 students on the Westville campus of the University of KwaZulu-Natal, South Africa. Two Information Communication Services (lCS) staff members were interviewed to gain insights into how the Wi-Fi was set up, and their perspectives on how students utilise the Wi-Fi. The questionnaire data were analysed statistically, and interview results were used to explain results. The students' most used venues, and the places they encountered poor and best Wi-Fi signal quality, are presented, along with the durations of use and problems encountered. When analysing these results by students' residence type, each category showed a different pattern of use. These results can help IT administrators understand where to improve the Wi-Fi quality, if necessary. It is particularly useful if some categories of students return to campus, while others do not, e.g. as COVID-19 lockdowns ease.},
  year = {2021},
  journal = {2021 International Conference on Artificial Intelligence, Big Data, Computing and Data Communication Systems (icABCD)},
  month = {5-6/08},
  publisher = {IEEE},
  address = {Durban, South Africa},
  isbn = {978-1-7281-8591-0},
  url = {https://ieeexplore.ieee.org/document/9519327},
  doi = {https://doi.org/10.1109/icABCD51485.2021.9519327},
}
1.
Heyninck J, Thimm M, Kern-Isberner G, Rienstra T, Skiba K. On the Relation between Possibilistic Logic and Abstract Dialectical Frameworks. 2021. https://sites.google.com/view/nmr2021/home?authuser=0).

Abstract dialectical frameworks (in short, ADFs) are one of the most general and unifying approaches to formal argumentation. As the semantics of ADFs are based on three-valued interpretations, the question poses itself as to whether some and which monotonic three-valued logic underlies ADFs, in the sense that it allows to capture the main semantic concepts underlying ADFs. As an entry-point for such an investigation, we take the concept of model of an ADF, which was originally formulated on the basis of Kleene’s three-valued logic. We show that an optimal concept of a model arises when instead of Kleene’s three-valued logic, possibilistic logic is used. We then show that in fact, possibilistic logic is the most conservative three-valued logic that fulfils this property, and that possibilistic logic can faithfully encode all other semantical concepts for ADFs. Based on this result, we also make some observations on strong equivalence and introduce possibilistic ADFs.

@misc{422,
  author = {Jesse Heyninck and Matthias Thimm and Gabriele Kern-Isberner and Tjitze Rienstra and Kenneth Skiba},
  title = {On the Relation between Possibilistic Logic and Abstract Dialectical Frameworks},
  abstract = {Abstract dialectical frameworks (in short, ADFs) are one of the most general and unifying approaches to formal argumentation. As the semantics of ADFs are based on three-valued interpretations, the question poses itself as to whether some and which monotonic three-valued logic underlies ADFs, in the sense that it allows to capture the main semantic concepts underlying ADFs. As an entry-point for such an investigation, we take the concept of model of an ADF, which was originally formulated on the basis of Kleene’s three-valued logic. We show that an optimal concept of a model arises when instead of Kleene’s three-valued logic, possibilistic logic is used. We then show that in fact, possibilistic logic is the most conservative three-valued logic that fulfils this property, and that possibilistic logic can faithfully encode all other semantical concepts for ADFs. Based on this result, we also make some observations on strong equivalence and introduce possibilistic ADFs.},
  year = {2021},
  url = {https://sites.google.com/view/nmr2021/home?authuser=0)},
}
1.
Heyninck J, Thimm M, Kern-Isberner G, Rienstra T, Skiba K. Arguing about Complex Formulas: Generalizing Abstract Dialectical Frameworks. 2021. https://sites.google.com/view/nmr2021/home?authuser=0.

Abstract dialectical frameworks (in short, ADFs) are a unifying model of formal argumentation, where argumentative relations between arguments are represented by assigning acceptance conditions to atomic arguments. This idea is generalized by letting acceptance conditions being assigned to complex formulas, resulting in conditional abstract dialectical frameworks (in short, cADFs). We define the semantics of cADFs in terms of a non-truth-functional four-valued logic, and study the semantics in-depth, by showing existence results and proving that all semantics are generalizations of the corresponding semantics for ADFs.

@misc{421,
  author = {Jesse Heyninck and Matthias Thimm and Gabriele Kern-Isberner and Tjitze Rienstra and Kenneth Skiba},
  title = {Arguing about Complex Formulas: Generalizing Abstract Dialectical Frameworks},
  abstract = {Abstract dialectical frameworks (in short, ADFs) are a unifying model of formal argumentation, where argumentative relations between arguments are represented by assigning acceptance conditions to atomic arguments. This idea is generalized by letting acceptance conditions being assigned to complex formulas, resulting in conditional abstract dialectical frameworks (in short, cADFs). We define the semantics of cADFs in terms of a non-truth-functional four-valued
logic, and study the semantics in-depth, by showing existence results and proving that all semantics are generalizations of the corresponding semantics for ADFs.},
  year = {2021},
  url = {https://sites.google.com/view/nmr2021/home?authuser=0},
}
1.
Heyninck J, Arieli O. Approximation Fixpoint Theory for Non-Deterministic Operators and Its Application in Disjunctive Logic Programming. In: 18th International Conference on Principles of Knowledge Representation and Reasoning. Online: IJCAI Organization; 2021. doi:10.24963/kr.2021/32.

Approximation fixpoint theory (AFT) constitutes an abstract and general algebraic framework for studying the semantics of nonmonotonic logics. It provides a unifying study of the semantics of different formalisms for nonmonotonic reasoning, such as logic programming, default logic and autoepistemic logic. In this paper we extend AFT to non-deterministic constructs such as disjunctive information. This is done by generalizing the main constructions and corresponding results to non-deterministic operators, whose ranges are sets of elements rather than single elements. The applicability and usefulness of this generalization is illustrated in the context of disjunctive logic programming.

@{420,
  author = {Jesse Heyninck and Ofer Arieli},
  title = {Approximation Fixpoint Theory for Non-Deterministic Operators and Its Application in Disjunctive Logic Programming},
  abstract = {Approximation fixpoint theory (AFT) constitutes an abstract and general algebraic framework for studying the semantics of nonmonotonic logics. It provides a unifying study of the semantics of different formalisms for nonmonotonic reasoning, such as logic programming, default logic and autoepistemic logic. In this paper we extend AFT to non-deterministic constructs such as disjunctive information. This is done by generalizing the main constructions and corresponding results to non-deterministic operators, whose ranges are sets of elements rather than single elements. The applicability and usefulness of this generalization is illustrated in the context of disjunctive logic programming.},
  year = {2021},
  journal = {18th International Conference on Principles of Knowledge Representation and Reasoning},
  pages = {334-344},
  month = {03/11-12/11},
  publisher = {IJCAI Organization},
  address = {Online},
  isbn = {978-1-956792-99-7},
  url = {https://proceedings.kr.org/2021/32/},
  doi = {10.24963/kr.2021/32},
}
1.
Heyninck J, Kern-Isberner G, Rienstra T, Skiba K, Thimm M. Revision and Conditional Inference for Abstract Dialectical Frameworks. In: 18th International Conference on Principles of Knowledge Representation and Reasoning. Online: IJCAI Organization; 2021. doi:10.24963/kr.2021/33.

For propositional beliefs, there are well-established connections between belief revision, defeasible conditionals and nonmonotonic inference. In argumentative contexts, such connections have not yet been investigated. On the one hand, the exact relationship between formal argumentation and nonmonotonic inference relations is a research topic that keeps on eluding researchers despite recently intensified efforts, whereas argumentative revision has been studied in numerous works during recent years. In this paper, we show that similar relationships between belief revision, defeasible conditionals and nonmonotonic inference hold in argumentative contexts as well. We first define revision operators for abstract dialectical frameworks, and use such revision operators to define dynamic conditionals by means of the Ramsey test. We show that such conditionals can be equivalently defined using a total preorder over three-valued interpretations, and study the inferential behaviour of the resulting conditional inference relations.

@{418,
  author = {Jesse Heyninck and Gabriele Kern-Isberner and Tjitze Rienstra and Kenneth Skiba and Matthias Thimm},
  title = {Revision and Conditional Inference for Abstract Dialectical Frameworks},
  abstract = {For propositional beliefs, there are well-established connections between belief revision, defeasible conditionals and
nonmonotonic inference. In argumentative contexts, such connections have not yet been investigated. On the one hand, the exact relationship between formal argumentation and nonmonotonic inference relations is a research topic that keeps on eluding researchers despite recently intensified efforts, whereas argumentative revision has been studied in numerous works during recent years. In this paper, we show that similar relationships between belief revision, defeasible conditionals and nonmonotonic inference hold in argumentative contexts as well. We first define revision operators for abstract dialectical frameworks, and use such revision operators to define dynamic conditionals by means of the Ramsey test. We show that such conditionals can be equivalently defined using a total preorder over three-valued interpretations, and study the inferential behaviour of the resulting conditional inference relations.},
  year = {2021},
  journal = {18th International Conference on Principles of Knowledge Representation and Reasoning},
  pages = {345-355},
  month = {03/11-12/11},
  publisher = {IJCAI Organization},
  address = {Online},
  isbn = {978-1-956792-99-7},
  url = {https://proceedings.kr.org/2021/33/},
  doi = {10.24963/kr.2021/33},
}
1.
Tollon F. Designed to Seduce: Epistemically Retrograde Ideation and YouTube’s Recommender System. International Journal of Technoethics (IJT). 2021;12 (2). doi:10.4018/IJT.2021070105.

Up to 70% of all watch time on YouTube is due to the suggested content of its recommender system. This system has been found, by virtue of its design, to be promoting conspiratorial content. In this paper, the author firstly critiques the value neutrality thesis regarding technology, showing it to be philosophically untenable. This means that technological artefacts can influence what people come to value (or perhaps even embody values themselves) and change the moral evaluation of an action. Secondly, he introduces the concept of an affordance, borrowed from the literature on ecological psychology. This concept allows him to make salient how technologies come to solicit certain kinds of actions from users, making such actions more or less likely, and in this way influencing the kinds of things one comes to value. Thirdly, he critically assesses the results of a study by Alfano et al. He makes use of the literature on affordances, introduced earlier, to shed light on how these technological systems come to mediate our perception of the world and influence action.

@article{415,
  author = {Fabio Tollon},
  title = {Designed to Seduce: Epistemically Retrograde Ideation and YouTube's Recommender System},
  abstract = {Up to 70% of all watch time on YouTube is due to the suggested content of its recommender system. This system has been found, by virtue of its design, to be promoting conspiratorial content. In this paper, the author firstly critiques the value neutrality thesis regarding technology, showing it to be philosophically untenable. This means that technological artefacts can influence what people come to value (or perhaps even embody values themselves) and change the moral evaluation of an action. Secondly, he introduces the concept of an affordance, borrowed from the literature on ecological psychology. This concept allows him to make salient how technologies come to solicit certain kinds of actions from users, making such actions more or less likely, and in this way influencing the kinds of things one comes to value. Thirdly, he critically assesses the results of a study by Alfano et al. He makes use of the literature on affordances, introduced earlier, to shed light on how these technological systems come to mediate our perception of the world and influence action.},
  year = {2021},
  journal = {International Journal of Technoethics (IJT)},
  volume = {12},
  issue = {2},
  publisher = {IGI Global},
  isbn = {9781799861492},
  url = {https://www.igi-global.com/gateway/article/281077},
  doi = {10.4018/IJT.2021070105},
}
1.
Tollon F. Artifacts and affordances: from designed properties to possibilities for action. AI & SOCIETY Journal of Knowledge, Culture and Communication. 2021;36(1). doi:https://doi.org/10.1007/s00146-021-01155-7.

In this paper I critically evaluate the value neutrality thesis regarding technology, and find it wanting. I then introduce the various ways in which artifacts can come to influence moral value, and our evaluation of moral situations and actions. Here, following van de Poel and Kroes, I introduce the idea of value sensitive design. Specifically, I show how by virtue of their designed properties, artifacts may come to embody values. Such accounts, however, have several shortcomings. In agreement with Michael Klenk, I raise epistemic and metaphysical issues with respect to designed properties embodying value. The concept of an affordance, borrowed from ecological psychology, provides a more philosophically fruitful grounding to the potential way(s) in which artifacts might embody values. This is due to the way in which it incorporates key insights from perception more generally, and how we go about determining possibilities for action in our environment specifically. The affordance account as it is presented by Klenk, however, is insufficient. I therefore argue that we understand affordances based on whether they are meaningful, and, secondly, that we grade them based on their force.

@article{386,
  author = {Fabio Tollon},
  title = {Artifacts and affordances: from designed properties to possibilities for action},
  abstract = {In this paper I critically evaluate the value neutrality thesis regarding technology, and find it wanting. I then introduce the various ways in which artifacts can come to influence moral value, and our evaluation of moral situations and actions. Here, following van de Poel and Kroes, I introduce the idea of value sensitive design. Specifically, I show how by virtue of their designed properties, artifacts may come to embody values. Such accounts, however, have several shortcomings. In agreement with Michael Klenk, I raise epistemic and metaphysical issues with respect to designed properties embodying value. The concept of an affordance, borrowed from ecological psychology, provides a more philosophically fruitful grounding to the potential way(s) in which artifacts might embody values. This is due to the way in which it incorporates key insights from perception more generally, and how we go about determining possibilities for action in our environment specifically. The affordance account as it is presented by Klenk, however, is insufficient. I therefore argue that we understand affordances based on whether they are meaningful, and, secondly, that we grade them based on their force.},
  year = {2021},
  journal = {AI & SOCIETY Journal of Knowledge, Culture and Communication},
  volume = {36},
  issue = {1},
  publisher = {Springer},
  url = {https://link.springer.com/article/10.1007%2Fs00146-021-01155-7},
  doi = {https://doi.org/10.1007/s00146-021-01155-7},
}

2020

1.
van der Merwe A, Smuts H, Gerber A. Data Collection in an Information Systems Design Science Research Project. In: 49th Annual Conference of the Southern African Computer Lecturers’ Association (SACLA). Online: SACLA 2020 Organising Committee, Rhodes University, South Africa; 2020. https://sacla2020.ru.ac.za/docs/SACLA2020Proceedings.pdf.

Design science research (DSR) is a popular research approach used in information systems for the design, development and evaluation of artefacts. There is some guidance in the literature on how to conduct DSR as an approach to find solutions for wicked problems. Some of the areas with which students who are involved in DSR struggle are the confirmation of the problem and design and evaluation of the artefact. Hevner et al. [1] presented their conceptual model for DSR in 2004 and in this paper we use this seminal work as guidance to illustrate where there is potential for inclusion of data collection activities to address these three areas of concern. We also indicate the nature of the data collection that can be used during these phases. Lastly, we use some cases studies to map the areas that we have identified to these case studies as illustration.

@{452,
  author = {Alta van der Merwe and Hanlie Smuts and Aurona Gerber},
  title = {Data Collection in an Information Systems Design Science Research Project},
  abstract = {Design science research (DSR) is a popular research approach used in information systems for the design, development and evaluation of artefacts. There is some guidance in the literature on how to conduct DSR as an approach to find solutions for wicked problems. Some of the areas with which students who are involved in DSR struggle are the confirmation of the problem and design and evaluation of the artefact. Hevner et al. [1] presented their conceptual model for DSR in 2004 and in this paper we use this seminal work as guidance to illustrate where there is potential for inclusion of data collection activities to
address these three areas of concern. We also indicate the nature of the data collection that can be used during these phases. Lastly, we use some cases studies to map the areas that we have identified to these case studies as illustration.},
  year = {2020},
  journal = {49th Annual Conference of the Southern African Computer Lecturers' Association (SACLA)},
  pages = {36-48},
  month = {06/07-09/07},
  publisher = {SACLA 2020 Organising Committee, Rhodes University, South Africa},
  address = {Online},
  isbn = {978-1-990964-40-4},
  url = {https://sacla2020.ru.ac.za/docs/SACLA2020Proceedings.pdf},
}
1.
Gerber A, le Roux P, Kearney C, van der Merwe A. The Zachman Framework for Enterprise Architecture: An Explanatory IS Theory. Lecture Notes in Computer Science. 2020;12066. doi:10.1007/978-3-030-44999-5_32.

Enterprise Architecture (EA) has had an interesting and often controversial history since its inception in the late 80’s by pioneers such as John Zachman. Zachman proposed the Zachman Framework for Enterprise Architecture (ZFEA), a descriptive, holistic representation of an enterprise for the purposes of providing insights and understanding. Some scholars claim that EA is an imperative to ensure successful business structures or business-IT alignment, or more recently with Enterprise Architecture Management (EAM), to manage required organizational transformation. However, EA initiatives within companies are often costly and the expected return on investment is not realized. In fact, Gartner recently indicated in their 2018 Enterprise Architecture Hype Cycle that EA is slowly emerging from the trough of disillusionment after nearly a decade. In this paper we argue that the role and value of EA is often misunderstood, and that EA, specifically the ZFEA for the purpose of this paper, could be considered as a theory given the view of theory within Information Systems (IS). The purpose of IS theories is to analyse, predict, explain and/or prescribe and it could be argued that EA often conform to these purposes. Using the taxonomy of theories as well as the structural components of theory within IS as proposed by Gregor, we motivate that the ZFEA could be regarded as an explanatory theory. Positioning ZFEA as IS explanatory theory provides insight into the role and purpose of the ZFEA (and by extension EA), and could assist researchers and practitioners with mediating the challenges experienced when instituting EA and EAM initiatives within organizations.

@article{441,
  author = {Aurona Gerber and Pierre le Roux and Carike Kearney and Alta van der Merwe},
  title = {The Zachman Framework for Enterprise Architecture: An Explanatory IS Theory},
  abstract = {Enterprise Architecture (EA) has had an interesting and often controversial history since its inception in the late 80’s by pioneers such as John Zachman. Zachman proposed the Zachman Framework for Enterprise Architecture (ZFEA), a descriptive, holistic representation of an enterprise for the purposes of providing insights and understanding. Some scholars claim that EA is an imperative to ensure successful business structures or business-IT alignment, or more recently with Enterprise Architecture Management (EAM), to manage required organizational transformation. However, EA initiatives within companies are often costly and the expected return on investment is not realized. In fact, Gartner recently indicated in their 2018 Enterprise Architecture Hype Cycle that EA is slowly emerging from the trough of disillusionment after nearly a decade. In this paper we argue that the role and value of EA is often misunderstood, and that EA, specifically the ZFEA for the purpose of this paper, could be considered as a theory given the view of theory within Information Systems (IS). The purpose of IS theories is to analyse, predict, explain and/or prescribe and it could be argued that EA often conform to these purposes. Using the taxonomy of theories as well as the structural components of theory within IS as proposed by Gregor, we motivate that the ZFEA could be regarded as an explanatory theory. Positioning ZFEA as IS explanatory theory provides insight into the role and purpose of the ZFEA (and by extension EA), and could assist researchers and practitioners with mediating the challenges experienced when instituting EA and EAM initiatives within organizations.},
  year = {2020},
  journal = {Lecture Notes in Computer Science},
  volume = {12066},
  pages = {383-396},
  publisher = {Springer},
  address = {Cham},
  isbn = {978-3-030-44999-5},
  url = {https://link.springer.com/chapter/10.1007/978-3-030-44999-5_32},
  doi = {10.1007/978-3-030-44999-5_32},
}
1.
Gerber A, le Roux P, van der Merwe A. Enterprise Architecture as Explanatory Information Systems Theory for Understanding Small- and Medium-Sized Enterprise Growth. Sustainability. 2020;12(20). doi:10.3390/su12208517.

Understanding and explaining small- and medium-sized enterprise (SME) growth is important for sustainability from multiple perspectives. Research indicates that SMEs comprise more than 80% of most economies, and their cumulative impact on sustainability considerations is far from trivial. In addition, for sustainability concerns to be prioritized, an SME has to be successful over time. In most developing countries, SMEs play a major role in solving socio-economic challenges. SMEs are an active research topic within the information systems (IS) discipline, often within the enterprise architecture (EA) domain. EA fundamentally adopts a systems perspective to describe the essential elements of a socio-technical organization and their relationships to each other and to the environment in order to understand complexity and manage change. However, despite rapid adoption originally, EA research and practice often fails to deliver on expectations. In some circles, EA became synonymous with projects that are over-budget, over-time and costly without the expected return on investment. In this paper, we argue that EA remains indispensable for understanding and explaining enterprises and that we fundamentally need to revisit some of the applications of EA. We, therefore, executed a research study in two parts. In the first part, we applied IS theory perspectives and adopted the taxonomy and structural components of theory to argue that EA, as represented by the Zachman Framework for Enterprise Architecture (ZFEA), could be adopted as an explanatory IS theory. In the second part of the study, we subsequently analysed multiple case studies from this theoretical basis to investigate whether distinguishable focus patterns could be detected during SME growth. The final results provide evidence that EA, represented through an appropriate framework like the ZFEA, could serve as an explanatory theory for SMEs during start-up, growth and transformation. We identified focus patterns and from these results, it should be possible to understand and explain how SMEs grow. Positioning the ZFEA as explanatory IS theory provides insight into the role and purpose of the ZFEA (and by extension EA), and could assist researchers and practitioners with mediating the challenges experienced by SMEs, and, by extension, enhance sustainable development.

@article{440,
  author = {Aurona Gerber and Pierre le Roux and Alta van der Merwe},
  title = {Enterprise Architecture as Explanatory Information Systems Theory for Understanding Small- and Medium-Sized Enterprise Growth},
  abstract = {Understanding and explaining small- and medium-sized enterprise (SME) growth is important for sustainability from multiple perspectives. Research indicates that SMEs comprise more than 80% of most economies, and their cumulative impact on sustainability considerations is far from trivial. In addition, for sustainability concerns to be prioritized, an SME has to be successful over time. In most developing countries, SMEs play a major role in solving socio-economic challenges. SMEs are an active research topic within the information systems (IS) discipline, often within the enterprise architecture (EA) domain. EA fundamentally adopts a systems perspective to describe the essential elements of a socio-technical organization and their relationships to each other and to the environment in order to understand complexity and manage change. However, despite rapid adoption originally, EA research and practice often fails to deliver on expectations. In some circles, EA became synonymous with projects that are over-budget, over-time and costly without the expected return on investment. In this paper, we argue that EA remains indispensable for understanding and explaining enterprises and that we fundamentally need to revisit some of the applications of EA. We, therefore, executed a research study in two parts. In the first part, we applied IS theory perspectives and adopted the taxonomy and structural components of theory to argue that EA, as represented by the Zachman Framework for Enterprise Architecture (ZFEA), could be adopted as an explanatory IS theory. In the second part of the study, we subsequently analysed multiple case studies from this theoretical basis to investigate whether distinguishable focus patterns could be detected during SME growth. The final results provide evidence that EA, represented through an appropriate framework like the ZFEA, could serve as an explanatory theory for SMEs during start-up, growth and transformation. We identified focus patterns and from these results, it should be possible to understand and explain how SMEs grow. Positioning the ZFEA as explanatory IS theory provides insight into the role and purpose of the ZFEA (and by extension EA), and could assist researchers and practitioners with mediating the challenges experienced by SMEs, and, by extension, enhance sustainable development.},
  year = {2020},
  journal = {Sustainability},
  volume = {12},
  issue = {20},
  isbn = {2071-1050},
  url = {https://www.mdpi.com/2071-1050/12/20/8517},
  doi = {10.3390/su12208517},
}
1.
Britz K, Casini G, Meyer T, Moodley K, Sattler U, Varzinczak I. Principles of KLM-style Defeasible Description Logics. Transactions on Computational Logic. 2020;22 (1). doi:10.1145/3420258.

The past 25 years have seen many attempts to introduce defeasible-reasoning capabilities into a description logic setting. Many, if not most, of these attempts are based on preferential extensions of description logics, with a significant number of these, in turn, following the so-called KLM approach to defeasible reasoning initially advocated for propositional logic by Kraus, Lehmann, and Magidor. Each of these attempts has its own aim of investigating particular constructions and variants of the (KLM-style) preferential approach. Here our aim is to provide a comprehensive study of the formal foundations of preferential defeasible reasoning for description logics in the KLM tradition. We start by investigating a notion of defeasible subsumption in the spirit of defeasible conditionals as studied by Kraus, Lehmann, and Magidor in the propositional case. In particular, we consider a natural and intuitive semantics for defeasible subsumption, and we investigate KLM-style syntactic properties for both preferential and rational subsumption. Our contribution includes two representation results linking our semantic constructions to the set of preferential and rational properties considered. Besides showing that our semantics is appropriate, these results pave the way for more effective decision procedures for defeasible reasoning in description logics. Indeed, we also analyse the problem of non-monotonic reasoning in description logics at the level of entailment and present an algorithm for the computation of rational closure of a defeasible knowledge base. Importantly, our algorithm relies completely on classical entailment and shows that the computational complexity of reasoning over defeasible knowledge bases is no worse than that of reasoning in the underlying classical DL ALC.

@article{433,
  author = {Katarina Britz and Giovanni Casini and Tommie Meyer and Kody Moodley and Uli Sattler and Ivan Varzinczak},
  title = {Principles of KLM-style Defeasible Description Logics},
  abstract = {The past 25 years have seen many attempts to introduce defeasible-reasoning capabilities into a description logic setting. Many, if not most, of these attempts are based on preferential extensions of description logics, with a significant number of these, in turn, following the so-called KLM approach to defeasible reasoning initially advocated for propositional logic by Kraus, Lehmann, and Magidor. Each of these attempts has its own aim of investigating particular constructions and variants of the (KLM-style) preferential approach. Here our aim is to provide a comprehensive study of the formal foundations of preferential defeasible reasoning for description logics in the KLM tradition. We start by investigating a notion of defeasible subsumption in the spirit of defeasible conditionals as studied by Kraus, Lehmann, and Magidor in the propositional case. In particular, we consider a natural and intuitive semantics for defeasible subsumption, and we investigate KLM-style syntactic properties for both preferential and rational subsumption. Our contribution includes two representation results linking our semantic
constructions to the set of preferential and rational properties considered. Besides showing that our semantics is appropriate, these results pave the way for more effective decision procedures for defeasible reasoning in description logics. Indeed, we also analyse the problem of non-monotonic reasoning in description logics at the level of entailment and present an algorithm for the computation of rational closure of a defeasible knowledge base. Importantly, our algorithm relies completely on classical entailment and shows that the computational complexity of reasoning over defeasible knowledge bases is no worse than that of reasoning in the underlying classical DL ALC.},
  year = {2020},
  journal = {Transactions on Computational Logic},
  volume = {22 (1)},
  pages = {1-46},
  publisher = {ACM},
  url = {https://dl-acm-org.ezproxy.uct.ac.za/doi/abs/10.1145/3420258},
  doi = {10.1145/3420258},
}
1.
Botha L, Meyer T, Penaloza R. The Probabilistic Description Logic BALC. Theory and Practice of Logic Programming. 2020. doi:10.1017/S1471068420000460.

Description logics (DLs) are well-known knowledge representation formalisms focused on the representation of terminological knowledge. Due to their first-order semantics, these languages (in their classical form) are not suitable for representing and handling uncertainty. A probabilistic extension of a light-weight DL was recently proposed for dealing with certain knowledge occurring in uncertain contexts. In this paper, we continue that line of research by introducing the Bayesian extension BALC of the propositionally closed DL ALC. We present a tableau-based procedure for deciding consistency and adapt it to solve other probabilistic, contextual, and general inferences in this logic. We also show that all these problems remain ExpTime-complete, the same as reasoning in the underlying classical ALC.

@article{432,
  author = {Leonard Botha and Tommie Meyer and Rafael Penaloza},
  title = {The Probabilistic Description Logic BALC},
  abstract = {Description logics (DLs) are well-known knowledge representation formalisms focused on the representation of terminological knowledge. Due to their first-order semantics, these languages (in their classical form) are not suitable for representing and handling uncertainty. A probabilistic extension of a light-weight DL was recently proposed for dealing with certain knowledge occurring in uncertain contexts. In this paper, we continue that line of research by introducing the Bayesian extension BALC of the propositionally closed DL ALC. We present a tableau-based procedure for deciding consistency and adapt it to solve other probabilistic, contextual, and general inferences in this logic. We also show that all these problems remain ExpTime-complete,
the same as reasoning in the underlying classical ALC.},
  year = {2020},
  journal = {Theory and Practice of Logic Programming},
  pages = {1-24},
  publisher = {Cambridge University Press},
  doi = {10.1017/S1471068420000460},
}
1.
Borgwardt S, Meyer T. Proceedings of the 33rd International Workshop on Description Logics (DL 2020). In: 33rd International Workshop on Description Logics (DL 2020). Online; 2020. http://ceur-ws.org/Vol-2663/.

Not applicable.

@{431,
  author = {Stefan Borgwardt and Tommie Meyer},
  title = {Proceedings of the 33rd International Workshop on Description Logics (DL 2020)},
  abstract = {Not applicable.},
  year = {2020},
  journal = {33rd International Workshop on Description Logics (DL 2020)},
  month = {12/09/2020-14/09/2020},
  address = {Online},
  url = {http://ceur-ws.org/Vol-2663/},
}
1.
Kaliski A, Meyer T. Quo Vadis KLM-style Defeasible Reasoning?. In: First Southern African Conference for Artificial Intelligence Research. Virtual: SACAIR2020; 2020. https://2020.sacair.org.za/wp-content/uploads/2021/02/SACAIR_Proceedings-MainBook_Finv4_compressed.pdf?_ga=2.116601743.849395099.1621802506-572599210.1621419278.

The field of defeasible reasoning has a variety of frameworks, all of which are constructed with the view of codifying the patterns of common-sense reasoning inherent to human reasoning. One of these frameworks was first described by Kraus, Lehmann and Magidor, and is accordingly referred to as the KLM framework. Initially defined in propositional logic, it has since been imported into description and modal logics, and implemented into many defeasible reasoning engines. However, there are many ways in which this framework may be advanced theoretically, and many opportunities for it to be applied. This paper covers some of the most prominent areas of future work and possible applications of this framework, with the intention that anyone who has recently familiarized themselves with this approach may then have an understanding of the kind of work in which they could engage.

@{414,
  author = {Adam Kaliski and Tommie Meyer},
  title = {Quo Vadis KLM-style Defeasible Reasoning?},
  abstract = {The field of defeasible reasoning has a variety of frameworks, all of which are constructed with the view of codifying the patterns of common-sense reasoning inherent to human reasoning. One of these frameworks was first described by Kraus, Lehmann and Magidor, and is accordingly referred to as the KLM framework. Initially defined in propositional logic, it has since been imported into description and modal logics, and implemented into many defeasible reasoning engines. However, there are many ways in which this framework may be advanced theoretically, and many opportunities for it to be applied. This paper covers some of the most prominent areas of future work and possible applications of this framework, with the intention that anyone who has recently familiarized themselves with this approach may then have an understanding of the kind of work in which they could engage.},
  year = {2020},
  journal = {First Southern African Conference for Artificial Intelligence Research},
  pages = {231-246},
  month = {22/02/2021},
  publisher = {SACAIR2020},
  address = {Virtual},
  isbn = {978-0-620-89373-2},
  url = {https://2020.sacair.org.za/wp-content/uploads/2021/02/SACAIR_Proceedings-MainBook_Finv4_compressed.pdf?_ga=2.116601743.849395099.1621802506-572599210.1621419278},
}
1.
Paterson-Jones G, Meyer T. A Boolean Extension of KLM-style Conditional Reasoning. In: First Southern African Conference for AI Research (SACAIR 2020). Muldersdrift, South Africa: Springer; 2020. doi:10.1007/978-3-030-66151-9_15.

Propositional KLM-style defeasible reasoning involves extending propositional logic with a new logical connective that can express defeasible (or conditional) implications, with semantics given by ordered structures known as ranked interpretations. KLM-style defeasible entailment is referred to as rational whenever the defeasible entailment relation under consideration generates a set of defeasible implications all satisfying a set of rationality postulates known as the KLM postulates. In a recent paper Booth et al. proposed PTL, a logic that is more expressive than the core KLM logic. They proved an impossibility result, showing that defeasible entailment for PTL fails to satisfy a set of rationality postulates similar in spirit to the KLM postulates. Their interpretation of the impossibility result is that defeasible entailment for PTL need not be unique. In this paper we continue the line of research in which the expressivity of the core KLM logic is extended. We present the logic Boolean KLM (BKLM) in which we allow for disjunctions, conjunctions, and negations, but not nesting, of defeasible implications. Our contribution is twofold. Firstly, we show (perhaps surprisingly) that BKLM is more expressive than PTL. Our proof is based on the fact that BKLM can characterise all single ranked interpretations, whereas PTL cannot. Secondly, given that the PTL impossibility result also applies to BKLM, we adapt the different forms of PTL entailment proposed by Booth et al. to apply to BKLM.

@{413,
  author = {Guy Paterson-Jones and Tommie Meyer},
  title = {A Boolean Extension of KLM-style Conditional Reasoning},
  abstract = {Propositional KLM-style defeasible reasoning involves extending propositional logic with a new logical connective that can express defeasible (or conditional) implications, with semantics given by ordered structures known as ranked interpretations. KLM-style defeasible entailment is referred to as rational whenever the defeasible entailment relation under consideration generates a set of defeasible implications all satisfying a set of rationality postulates known as the KLM postulates. In a recent paper Booth et al. proposed PTL, a logic that is more expressive than the core KLM logic. They proved an impossibility result, showing that defeasible entailment for PTL fails to satisfy a set of rationality postulates similar in spirit to the KLM postulates. Their interpretation of the impossibility result is that defeasible entailment for PTL need not be unique. In this paper we continue the line of research in which the expressivity of the core KLM logic is extended. We present the logic Boolean KLM (BKLM) in which we allow for disjunctions, conjunctions, and negations, but not nesting, of defeasible implications. Our contribution is twofold. Firstly, we show (perhaps surprisingly) that BKLM is more expressive than PTL. Our proof is based on the fact that BKLM can characterise all single ranked interpretations, whereas PTL cannot. Secondly, given that the PTL impossibility result also applies to BKLM, we adapt the different forms of PTL entailment proposed by Booth et al. to apply to BKLM.},
  year = {2020},
  journal = {First Southern African Conference for AI Research (SACAIR 2020)},
  pages = {236-252},
  month = {22/02/2021-26/02/2021},
  publisher = {Springer},
  address = {Muldersdrift, South Africa},
  isbn = {978-3-030-66151-9},
  url = {https://link.springer.com/book/10.1007/978-3-030-66151-9},
  doi = {10.1007/978-3-030-66151-9_15},
}
1.
Baker CK, Denny C, Freund P, Meyer T. Cognitive Defeasible Reasoning: the Extent to which Forms of Defeasible Reasoning Correspond with Human Reasoning. In: First Southern African Conference for AI Research (SACAIR 2020). Muldersdrift, South Africa: Springer; 2020. doi:10.1007/978-3-030-66151-9_13.

Classical logic forms the basis of knowledge representation and reasoning in AI. In the real world, however, classical logic alone is insufficient to describe the reasoning behaviour of human beings. It lacks the flexibility so characteristically required of reasoning under uncertainty, reasoning under incomplete information and reasoning with new information, as humans must. In response, non-classical extensions to propositional logic have been formulated, to provide non-monotonicity. It has been shown in previous studies that human reasoning exhibits non-monotonicity. This work is the product of merging three independent studies, each one focusing on a different formalism for non-monotonic reasoning: KLM defeasible reasoning, AGM belief revision and KM belief update. We investigate, for each of the postulates propounded to characterise these logic forms, the extent to which they have correspondence with human reasoners. We do this via three respective experiments and present each of the postulates in concrete and abstract form. We discuss related work, our experiment design, testing and evaluation, and report on the results from our experiments. We find evidence to believe that 1 out of 5 KLM defeasible reasoning postulates, 3 out of 8 AGM belief revision postulates and 4 out of 8 KM belief update postulates conform in both the concrete and abstract case. For each experiment, we performed an additional investigation. In the experiments of KLM defeasible reasoning and AGM belief revision, we analyse the explanations given by participants to determine whether the postulates have a normative or descriptive relationship with human reasoning. We find evidence that suggests, overall, KLM defeasible reasoning has a normative relationship with human reasoning while AGM belief revision has a descriptive relationship with human reasoning. In the experiment of KM belief update, we discuss counter-examples to the KM postulates.

@{412,
  author = {Clayton Baker and Claire Denny and Paul Freund and Tommie Meyer},
  title = {Cognitive Defeasible Reasoning: the Extent to which Forms of Defeasible Reasoning Correspond with Human Reasoning},
  abstract = {Classical logic forms the basis of knowledge representation and reasoning in AI. In the real world, however, classical logic alone is insufficient to describe the reasoning behaviour of human beings. It lacks the flexibility so characteristically required of reasoning under uncertainty, reasoning under incomplete information and reasoning with new information, as humans must. In response, non-classical extensions to propositional logic have been formulated, to provide non-monotonicity. It has been shown in previous studies that human reasoning exhibits non-monotonicity. This work is the product of merging three independent studies, each one focusing on a different formalism for non-monotonic reasoning: KLM defeasible reasoning, AGM belief revision and KM belief update. We investigate, for each of the postulates propounded to characterise these logic forms, the extent to which they have correspondence with human reasoners. We do this via three respective experiments and present each of the postulates in concrete and abstract form. We discuss related work, our experiment design, testing and evaluation, and report on the results from our experiments. We find evidence to believe that 1 out of 5 KLM defeasible reasoning postulates, 3 out of 8 AGM belief revision postulates and 4 out of 8 KM belief update postulates conform in both the concrete and abstract case. For each experiment, we performed an additional investigation. In the experiments of KLM defeasible reasoning and AGM belief revision, we analyse the explanations given by participants to determine whether the postulates have a normative or descriptive relationship with human reasoning. We find evidence that suggests, overall, KLM defeasible reasoning has a normative relationship with human reasoning while AGM belief revision has a descriptive relationship with human reasoning. In the experiment of KM belief update, we discuss counter-examples to the KM postulates.},
  year = {2020},
  journal = {First Southern African Conference for AI Research (SACAIR 2020)},
  pages = {199-219},
  month = {22/02/2021-26/02/2021},
  publisher = {Springer},
  address = {Muldersdrift, South Africa},
  isbn = {978-3-030-66151-9},
  url = {https://link.springer.com/book/10.1007/978-3-030-66151-9},
  doi = {10.1007/978-3-030-66151-9_13},
}
1.
Harrison M, Meyer T. DDLV: A System for rational preferential reasoning for datalog. South African Computer Journal. 2020;32(2). doi:10.18489/sacj.v32i2.850.

Datalog is a powerful language that can be used to represent explicit knowledge and compute inferences in knowledge bases. Datalog cannot, however, represent or reason about contradictory rules. This is a limitation as contradictions are often present in domains that contain exceptions. In this paper, we extend Datalog to represent contradictory and defeasible information. We define an approach to efficiently reason about contradictory information in Datalog and show that it satisfies the KLM requirements for a rational consequence relation. We introduce DDLV, a defeasible Datalog reasoning system that implements this approach. Finally, we evaluate the performance of DDLV.

@article{411,
  author = {Michael Harrison and Tommie Meyer},
  title = {DDLV: A System for rational preferential reasoning for datalog},
  abstract = {Datalog is a powerful language that can be used to represent explicit knowledge and compute inferences in knowledge bases. Datalog cannot, however, represent or reason about contradictory rules. This is a limitation as contradictions are often present in domains that contain exceptions. In this paper, we extend Datalog to represent contradictory and defeasible information. We define an approach to efficiently reason about contradictory information in Datalog and show that it satisfies the KLM requirements for a rational consequence relation. We introduce DDLV, a defeasible Datalog reasoning system that implements this approach. Finally, we evaluate the performance of DDLV.},
  year = {2020},
  journal = {South African Computer Journal},
  volume = {32},
  pages = {184-217},
  issue = {2},
  publisher = {SACJ},
  address = {Online},
  isbn = {ISSN 2313-7835},
  doi = {10.18489/sacj.v32i2.850},
}
1.
Chingoma J, Meyer T. Defeasibility applied to Forrester’s paradox. South African Computer Journal. 2020;32(2). doi:10.18489/sacj.v32i2.848.

Deontic logic is a logic often used to formalise scenarios in the legal domain. Within the legal domain there are many exceptions and conflicting obligations. This motivates the enrichment of deontic logic with not only the notion of defeasibility, which allows for reasoning about exceptions, but a stronger notion of typicality that is based on defeasibility. KLM-style defeasible reasoning is a logic system that employs defeasibility while Propositional Typicality Logic (PTL) is a logic that does the same for the notion of typicality. Deontic paradoxes are often used to examine logic systems as the paradoxes provide undesirable results even if the scenarios seem intuitive. Forrester’s paradox is one of the most famous of these paradoxes. This paper shows that KLM-style defeasible reasoning and PTL can be used to represent and reason with Forrester’s paradox in such a way as to block undesirable conclusions without completely sacrificing desirable deontic properties.

@article{410,
  author = {Julian Chingoma and Tommie Meyer},
  title = {Defeasibility applied to Forrester’s paradox},
  abstract = {Deontic logic is a logic often used to formalise scenarios in the legal domain. Within the legal domain there are many exceptions and conflicting obligations. This motivates the enrichment of deontic logic with not only the notion of defeasibility, which allows for reasoning about exceptions, but a stronger notion of typicality that is based on defeasibility. KLM-style defeasible reasoning is a logic system that employs defeasibility while Propositional Typicality Logic (PTL) is a logic that does the same for the notion of typicality. Deontic paradoxes are often used to examine logic systems as the paradoxes provide undesirable results even if the scenarios seem intuitive. Forrester’s paradox is one of the most famous of these paradoxes. This paper shows that KLM-style defeasible reasoning and PTL can be used to represent and reason with Forrester’s paradox in such a way as to block undesirable conclusions without completely sacrificing desirable deontic properties.},
  year = {2020},
  journal = {South African Computer Journal},
  volume = {32},
  pages = {161-183},
  issue = {2},
  publisher = {SACJ},
  address = {Online},
  isbn = {ISSN 2313-7835},
  doi = {10.18489/sacj.v32i2.848},
}
1.
Morris M, Ross T, Meyer T. Algorithmic definitions for KLM-style defeasible disjunctive Datalog. South African Computer Journal. 2020;32(2). doi:10.18489/sacj.v32i2.846.

Datalog is a declarative logic programming language that uses classical logical reasoning as its basic form of reasoning. Defeasible reasoning is a form of non-classical reasoning that is able to deal with exceptions to general assertions in a formal manner. The KLM approach to defeasible reasoning is an axiomatic approach based on the concept of plausible inference. Since Datalog uses classical reasoning, it is currently not able to handle defeasible implications and exceptions. We aim to extend the expressivity of Datalog by incorporating KLM-style defeasible reasoning into classical Datalog. We present a systematic approach for extending the KLM properties and a well-known form of defeasible entailment: Rational Closure. We conclude by exploring Datalog extensions of less conservative forms of defeasible entailment: Relevant and Lexicographic Closure. We provide algorithmic definitions for these forms of defeasible entailment and prove that the definitions are LM-rational.

@article{409,
  author = {Matthew Morris and Tala Ross and Tommie Meyer},
  title = {Algorithmic definitions for KLM-style defeasible disjunctive Datalog},
  abstract = {Datalog is a declarative logic programming language that uses classical logical reasoning as its basic form of reasoning. Defeasible reasoning is a form of non-classical reasoning that is able to deal with exceptions to general assertions in a formal manner. The KLM approach to defeasible reasoning is an axiomatic approach based on the concept of plausible inference. Since Datalog uses classical reasoning, it is currently not able to handle defeasible implications and exceptions. We aim to extend the expressivity of Datalog by incorporating KLM-style defeasible reasoning into classical Datalog. We present a systematic approach for extending the KLM properties and a well-known form of defeasible entailment: Rational Closure. We conclude by exploring Datalog extensions of less conservative forms of defeasible entailment: Relevant and Lexicographic Closure. We provide algorithmic definitions for these forms of defeasible entailment and prove that the definitions are LM-rational.},
  year = {2020},
  journal = {South African Computer Journal},
  volume = {32},
  pages = {141-160},
  issue = {2},
  publisher = {SACJ},
  address = {Online},
  isbn = {ISSN 2313-7835},
  doi = {10.18489/sacj.v32i2.846},
}
1.
Toussaint W, Moodley D. Clustering Residential Electricity Consumption Data to Create Archetypes that Capture Household Behaviour in South Africa. South African Computer Journal. 2020;32(2). doi:http://dx.doi.org/10.18489/sacj.v32i2.845 .

Clustering is frequently used in the energy domain to identify dominant electricity consumption patterns of households, which can be used to construct customer archetypes for long term energy planning. Selecting a useful set of clusters however requires extensive experimentation and domain knowledge. While internal clustering validation measures are well established in the electricity domain, they are limited for selecting useful clusters. Based on an application case study in South Africa, we present an approach for formalising implicit expert knowledge as external evaluation measures to create customer archetypes that capture variability in residential electricity consumption behaviour. By combining internal and external validation measures in a structured manner, we were able to evaluate clustering structures based on the utility they present for our application. We validate the selected clusters in a use case where we successfully reconstruct customer archetypes previously developed by experts. Our approach shows promise for transparent and repeatable cluster ranking and selection by data scientists, even if they have limited domain knowledge.

@article{408,
  author = {Wiebke Toussaint and Deshen Moodley},
  title = {Clustering Residential Electricity Consumption Data to Create Archetypes that Capture Household Behaviour in South Africa},
  abstract = {Clustering is frequently used in the energy domain to identify dominant electricity consumption patterns of households, which can be used to construct customer archetypes for long term energy planning. Selecting a useful set of clusters however requires extensive experimentation and domain knowledge. While internal clustering validation measures are well established in the electricity domain, they are limited for selecting useful clusters. Based on an application case study in South Africa, we present an approach for formalising implicit expert knowledge as external evaluation measures to create customer archetypes that capture variability in residential electricity consumption behaviour. By combining internal and external validation measures in a structured manner, we were able to evaluate clustering structures based on the utility they present for our application. We validate the selected clusters in a use case where we successfully reconstruct customer archetypes previously developed by experts. Our approach shows promise for transparent and repeatable cluster ranking and selection by data scientists, even if they have limited domain knowledge.},
  year = {2020},
  journal = {South African Computer Journal},
  volume = {32},
  pages = {1-34},
  issue = {2},
  publisher = {SACJ},
  address = {Online},
  isbn = {ISSN 2313-7835},
  url = {http://www.scielo.org.za/scielo.php?pid=S2313-78352020000200003&script=sci_arttext&tlng=en},
  doi = {http://dx.doi.org/10.18489/sacj.v32i2.845},
}
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