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Fabio Tollon is a doctoral candidate in philosophy of science at Bielefeld University. He believes that the development of AI will fundamentally change our moral landscape, both in terms of the number of action schemes available to us, and the potential implications of our actions. It is therefore essential that we have a robust meta-ethical grounding in our approach to the ethics of AI. Without rigorous conceptual apparatus we will be lost in our ethical analysis of these emergent and ubiquitous artificial systems. Fabio is currently part of the research training group GRK 2073 "Integrating Ethics and Epistemology of Scientific Research", funded by the German Research Foundation. His research focuses on the potential for artificial systems to be moral agents and/or moral patients, and what this could mean for scientists developing and using such systems. He has a BA PPE (politics, philosophy and economics), BA honours (philosophy), and an MA (philosophy), all from Stellenbosch University.
TALKS:
1) 'Toward a Coherent Account of Moral Agency' (FAIR 2019);
2) 'Functional Moral Agency' (4IR: Philosophical, Ethical and Legal Perspectives 2019).
PUBLICATIONS:
1) Tollon, Fabio. 2020. The Artificial View: toward a non-anthropocentric account of moral patiency. Ethics and Information Technology. https://doi.org/10.1007/s10676-020-09540-4;
2) Tollon, Fabio. 2019. Moral Agents or Mindless Machines? A critical appraisal of agency in artificial systems. Hungarian Philosophical Review 63(4), pp. 9-23;
3) Tollon, Fabio. 2019. Toward a Coherent Account of Moral Agency. Proceedings of the South African Forum for Artificial Intelligence Research. Vol 2540. http://ceur-ws.org/Vol-2540/.
TALKS:
1) 'Toward a Coherent Account of Moral Agency' (FAIR 2019);
2) 'Functional Moral Agency' (4IR: Philosophical, Ethical and Legal Perspectives 2019).
PUBLICATIONS:
1) Tollon, Fabio. 2020. The Artificial View: toward a non-anthropocentric account of moral patiency. Ethics and Information Technology. https://doi.org/10.1007/s10676-020-09540-4;
2) Tollon, Fabio. 2019. Moral Agents or Mindless Machines? A critical appraisal of agency in artificial systems. Hungarian Philosophical Review 63(4), pp. 9-23;
3) Tollon, Fabio. 2019. Toward a Coherent Account of Moral Agency. Proceedings of the South African Forum for Artificial Intelligence Research. Vol 2540. http://ceur-ws.org/Vol-2540/.
Latest Research Publications:
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},
}
Tollon F. The artifcial view: toward a non‑anthropocentric account of moral patiency. Ethics and Information Technology. 2020;22(4). doi:https://doi.org/10.1007/s10676-020-09540-4.
In this paper I provide an exposition and critique of the Organic View of Ethical Status, as outlined by Torrance (2008). A key presupposition of this view is that only moral patients can be moral agents. It is claimed that because artificial agents lack sentience, they cannot be proper subjects of moral concern (i.e. moral patients). This account of moral standing in principle excludes machines from participating in our moral universe. I will argue that the Organic View operationalises anthropocentric intuitions regarding sentience ascription, and by extension how we identify moral patients. The main difference between the argument I provide here and traditional arguments surrounding moral attributability is that I do not necessarily defend the view that internal states ground our ascriptions of moral patiency. This is in contrast to views such as those defended by Singer (1975, 2011) and Torrance (2008), where concepts such as sentience play starring roles. I will raise both conceptual and epistemic issues with regards to this sense of sentience. While this does not preclude the usage of sentience outright, it suggests that we should be more careful in our usage of internal mental states to ground our moral ascriptions. Following from this I suggest other avenues for further exploration into machine moral patiency which may not have the same shortcomings as the Organic View.
@article{387,
author = {Fabio Tollon},
title = {The artifcial view: toward a non‑anthropocentric account of moral patiency},
abstract = {In this paper I provide an exposition and critique of the Organic View of Ethical Status, as outlined by Torrance (2008). A key presupposition of this view is that only moral patients can be moral agents. It is claimed that because artificial agents lack sentience, they cannot be proper subjects of moral concern (i.e. moral patients). This account of moral standing in principle excludes machines from participating in our moral universe. I will argue that the Organic View operationalises anthropocentric intuitions regarding sentience ascription, and by extension how we identify moral patients. The main difference between the argument I provide here and traditional arguments surrounding moral attributability is that I do not necessarily defend the view that internal states ground our ascriptions of moral patiency. This is in contrast to views such as those defended by Singer (1975, 2011) and Torrance (2008), where concepts such as sentience play starring roles. I will raise both conceptual and epistemic issues with regards to this sense of sentience. While this does not preclude the usage of sentience outright, it suggests that we should be more careful in our usage of internal mental states to ground our moral ascriptions. Following from this I suggest other avenues for further exploration into machine moral patiency which may not have the same shortcomings as the Organic View.},
year = {2020},
journal = {Ethics and Information Technology},
volume = {22},
issue = {4},
publisher = {Springer},
url = {https://link.springer.com/article/10.1007%2Fs10676-020-09540-4},
doi = {https://doi.org/10.1007/s10676-020-09540-4},
}
Research Groups:
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My research interests include the application of machine learning to natural language processing and algorithmic complexity attacks, specifically regular expression denial of service attacks.
Latest Research Publications:
Berglund M, Drewes F, van der Merwe B. The Output Size Problem for String-to-Tree Transducers. Journal of Automata, Languages and Combinatorics. 2018;23(1). https://www.jalc.de/issues/2018/issue_23_1-3/jalc-2018-019-038.php.
The output size problem, for a string-to-tree transducer, is to determine the asymptotic behavior of the function describing the maximum size of output trees, with respect to the length of input strings. We show that the problem to determine, for a given regular expression, the worst-case matching time of a backtracking regular expression matcher, can be reduced to the output size problem. The latter can, in turn, be solved by determining the degree of ambiguity of a non-deterministic finite automaton.
Keywords: string-to-tree transducers, output size, backtracking regular expression matchers, NFA ambiguity
@article{201,
author = {Martin Berglund, F. Drewes, Brink van der Merwe},
title = {The Output Size Problem for String-to-Tree Transducers},
abstract = {The output size problem, for a string-to-tree transducer, is to determine the asymptotic behavior of the function describing the maximum size of output trees, with respect to the length of input strings. We show that the problem to determine, for a given regular expression, the worst-case matching time of a backtracking regular expression matcher, can be reduced to the output size problem. The latter can, in turn, be solved by determining the degree of ambiguity of a non-deterministic finite automaton.
Keywords: string-to-tree transducers, output size, backtracking regular expression matchers, NFA ambiguity},
year = {2018},
journal = {Journal of Automata, Languages and Combinatorics},
volume = {23},
pages = {19-38},
issue = {1},
publisher = {Institut für Informatik, Justus-Liebig-Universität Giessen},
address = {Germany},
isbn = {2567-3785},
url = {https://www.jalc.de/issues/2018/issue_23_1-3/jalc-2018-019-038.php},
}
Berglund M, Drewes F, van der Merwe B. On Regular Expressions with Backreferences and Transducers. In: 10th Workshop on Non-Classical Models of Automata and Applications (NCMA 2018). ; 2018.
Modern regular expression matching software features many extensions, some general while some are very narrowly speci ed. Here we consider the generalization of adding a class of operators which can be described by, e.g. nite-state transducers. Combined with backreferences they enable new classes of languages to be matched. The addition of nite-state transducers is shown to make membership testing undecidable. Following this result, we study the complexity of membership testing for various restricted cases of the model.
@{199,
author = {Martin Berglund, F. Drewes, Brink van der Merwe},
title = {On Regular Expressions with Backreferences and Transducers},
abstract = {Modern regular expression matching software features many extensions, some general while some are very narrowly speci ed. Here we consider the generalization of adding a class of operators which can be described by, e.g. nite-state transducers. Combined with backreferences they enable new classes of languages to be matched. The addition of nite-state transducers is shown to make membership testing undecidable. Following this result, we study the complexity of membership testing for various restricted cases of the model.},
year = {2018},
journal = {10th Workshop on Non-Classical Models of Automata and Applications (NCMA 2018)},
pages = {1-19},
month = {21/08-22/08},
}
van der Merwe B, Berglund M, Bester W. Formalising Boost POSIX Regular Expression Matching. In: International Colloquium on Theoretical Aspects of Computing. Springer; 2018. https://link.springer.com/chapter/10.1007/978-3-030-02508-3_6.
Whereas Perl-compatible regular expression matchers typically exhibit some variation of leftmost-greedy semantics, those conforming to the posix standard are prescribed leftmost-longest semantics. However, the posix standard leaves some room for interpretation, and Fowler and Kuklewicz have done experimental work to confirm differences between various posix matchers. The Boost library has an interesting take on the posix standard, where it maximises the leftmost match not with respect to subexpressions of the regular expression pattern, but rather, with respect to capturing groups. In our work, we provide the first formalisation of Boost semantics, and we analyse the complexity of regular expression matching when using Boost semantics.
@{196,
author = {Brink van der Merwe, Martin Berglund, Willem Bester},
title = {Formalising Boost POSIX Regular Expression Matching},
abstract = {Whereas Perl-compatible regular expression matchers typically exhibit some variation of leftmost-greedy semantics, those conforming to the posix standard are prescribed leftmost-longest semantics. However, the posix standard leaves some room for interpretation, and Fowler and Kuklewicz have done experimental work to confirm differences between various posix matchers. The Boost library has an interesting take on the posix standard, where it maximises the leftmost match not with respect to subexpressions of the regular expression pattern, but rather, with respect to capturing groups. In our work, we provide the first formalisation of Boost semantics, and we analyse the complexity of regular expression matching when using Boost semantics.},
year = {2018},
journal = {International Colloquium on Theoretical Aspects of Computing},
pages = {99-115},
month = {17/02},
publisher = {Springer},
isbn = {978-3-030-02508-3},
url = {https://link.springer.com/chapter/10.1007/978-3-030-02508-3_6},
}
van der Merwe B, Weideman N, Berglund M. Turning evil regexes harmless. In: Conference of South African Institute of Computer Scientists and Information Technologists (SAICSIT'17). ACM; 2017. https://dl.acm.org/citation.cfm?id=3129416.
No Abstract
@{178,
author = {Brink van der Merwe, N. Weideman, Martin Berglund},
title = {Turning evil regexes harmless},
abstract = {No Abstract},
year = {2017},
journal = {Conference of South African Institute of Computer Scientists and Information Technologists (SAICSIT'17)},
month = {26/09-28/09},
publisher = {ACM},
url = {https://dl.acm.org/citation.cfm?id=3129416},
}
Berglund M, van der Merwe B. Regular Expressions with Backreferences Re-examined. In: The Prague Stringology Conference (PSC 2017). Czech Technical University in Prague,; 2017.
Most modern regular expression matching libraries (one of the rare exceptions being Google’s RE2) allow backreferences, operations which bind a substring to a variable allowing it to be matched again verbatim. However, different implementations not only vary in the syntax permitted when using backreferences, but both implementations and definitions in the literature offer up a number of different variants on how backreferences match. Our aim is to compare the various flavors by considering the formal languages that each can describe, resulting in the establishment of a hierarchy of language classes. Beyond the hierarchy itself, some complexity results are given, and as part of the effort on comparing language classes new pumping lemmas are established, and old ones extended to new classes.
@{176,
author = {Martin Berglund, Brink van der Merwe},
title = {Regular Expressions with Backreferences Re-examined},
abstract = {Most modern regular expression matching libraries (one of the rare exceptions being Google’s RE2) allow backreferences, operations which bind a substring to a variable allowing it to be matched again verbatim. However, different implementations not only vary in the syntax permitted when using backreferences, but both implementations and definitions in the literature offer up a number of different variants on how backreferences match. Our aim is to compare the various flavors by considering the formal languages that each can describe, resulting in the establishment of a hierarchy of language classes. Beyond the hierarchy itself, some complexity results are given, and as part of the effort on comparing language classes new pumping lemmas are established, and old ones extended to new classes.},
year = {2017},
journal = {The Prague Stringology Conference (PSC 2017)},
pages = {30-41},
month = {28/08-30/08},
address = {Czech Technical University in Prague,},
isbn = {ISBN 978-80-01-06193-0},
}
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Latest Research Publications:
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Research Groups:
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Ivan José Varzinczak is a professor of computer science at Univ. d'Artois and member of CRIL Lab France. He holds a Ph.D. (2006) in Artificial Intelligence from Université Paul Sabatier, France, an M.Sc. (2002) and a B.Sc. (2000) both in Computer Science from the Federal University of Paraná, Brazil.
Ivan’s main research interest area is logic-based knowledge representation and reasoning in artificial intelligence, with focus on modal and description logics and their applications in non-monotonic reasoning, reasoning about actions and change, and the semantic web.
Ivan’s main research interest area is logic-based knowledge representation and reasoning in artificial intelligence, with focus on modal and description logics and their applications in non-monotonic reasoning, reasoning about actions and change, and the semantic web.
Latest Research Publications:
Casini G, Meyer T, Varzinczak I. Rational Defeasible Belief Change. In: 17th International Conference on Principles of Knowledge Representation and Reasoning (KR 2020). Virtual: IJCAI; 2020. doi:10.24963/kr.2020/22.
We present a formal framework for modelling belief change within a non-monotonic reasoning system. Belief change and non-monotonic reasoning are two areas that are formally closely related, with recent attention being paid towards the analysis of belief change within a non-monotonic environment. In this paper we consider the classical AGM belief change operators, contraction and revision, applied to a defeasible setting in the style of Kraus, Lehmann, and Magidor. The investigation leads us to the formal characterisation of a number of classes of defeasible belief change operators. For the most interesting classes we need to consider the problem of iterated belief change, generalising the classical work of Darwiche and Pearl in the process. Our work involves belief change operators aimed at ensuring logical consistency, as well as the characterisation of analogous operators aimed at obtaining coherence—an important notion within the field of logic-based ontologies
@{382,
author = {Giovanni Casini, Thomas Meyer, Ivan Varzinczak},
title = {Rational Defeasible Belief Change},
abstract = {We present a formal framework for modelling belief change within a non-monotonic reasoning system. Belief change and non-monotonic reasoning are two areas that are formally closely related, with recent attention being paid towards the analysis of belief change within a non-monotonic environment. In this paper we consider the classical AGM belief change operators, contraction and revision, applied to a defeasible setting in the style of Kraus, Lehmann, and Magidor. The investigation leads us to the formal characterisation of a number of classes of defeasible belief change operators. For the most interesting classes we need to consider the problem of iterated belief change, generalising the classical work of Darwiche and Pearl in the process. Our work involves belief change operators aimed at ensuring logical consistency, as well as the characterisation of analogous operators aimed at obtaining coherence—an important notion within the field of logic-based ontologies},
year = {2020},
journal = {17th International Conference on Principles of Knowledge Representation and Reasoning (KR 2020)},
pages = {213-222},
month = {12/09/2020},
publisher = {IJCAI},
address = {Virtual},
url = {https://library.confdna.com/kr/2020/},
doi = {10.24963/kr.2020/22},
}
Britz K, Varzinczak I. Preferential tableaux for contextual defeasible ALC. In: 28th International Conference on Automated Reasoning with Analytic Tableaux and Related Methods (TABLEAUX). Springer LNAI no. 11714; 2019. https://www.springer.com/gp/book/9783030290252.
In recent work, we addressed an important limitation in previous ex- tensions of description logics to represent defeasible knowledge, namely the re- striction in the semantics of defeasible concept inclusion to a single preference or- der on objects of the domain. Syntactically, this limitation translates to a context- agnostic notion of defeasible subsumption, which is quite restrictive when it comes to modelling different nuances of defeasibility. Our point of departure in our recent proposal allows for different orderings on the interpretation of roles. This yields a notion of contextual defeasible subsumption, where the context is informed by a role. In the present paper, we extend this work to also provide a proof-theoretic counterpart and associated results. We define a (naïve) tableau- based algorithm for checking preferential consistency of contextual defeasible knowledge bases, a central piece in the definition of other forms of contextual defeasible reasoning over ontologies, notably contextual rational closure.
@{247,
author = {Katarina Britz, Ivan Varzinczak},
title = {Preferential tableaux for contextual defeasible ALC},
abstract = {In recent work, we addressed an important limitation in previous ex- tensions of description logics to represent defeasible knowledge, namely the re- striction in the semantics of defeasible concept inclusion to a single preference or- der on objects of the domain. Syntactically, this limitation translates to a context- agnostic notion of defeasible subsumption, which is quite restrictive when it comes to modelling different nuances of defeasibility. Our point of departure in our recent proposal allows for different orderings on the interpretation of roles. This yields a notion of contextual defeasible subsumption, where the context is informed by a role. In the present paper, we extend this work to also provide a proof-theoretic counterpart and associated results. We define a (naïve) tableau- based algorithm for checking preferential consistency of contextual defeasible knowledge bases, a central piece in the definition of other forms of contextual defeasible reasoning over ontologies, notably contextual rational closure.},
year = {2019},
journal = {28th International Conference on Automated Reasoning with Analytic Tableaux and Related Methods (TABLEAUX)},
pages = {39-57},
month = {03/09-05/09},
publisher = {Springer LNAI no. 11714},
isbn = {ISBN 978-3-030-29026-9},
url = {https://www.springer.com/gp/book/9783030290252},
}
Britz K, Varzinczak I. Contextual rational closure for defeasible ALC. Annals of Mathematics and Artificial Intelligence. 2019;87(1-2). doi:10.1007/s10472-019-09658-2.
Description logics have been extended in a number of ways to support defeasible reason- ing in the KLM tradition. Such features include preferential or rational defeasible concept inclusion, and defeasible roles in complex concept descriptions. Semantically, defeasible subsumption is obtained by means of a preference order on objects, while defeasible roles are obtained by adding a preference order to role interpretations. In this paper, we address an important limitation in defeasible extensions of description logics, namely the restriction in the semantics of defeasible concept inclusion to a single preference order on objects. We do this by inducing a modular preference order on objects from each modular preference order on roles, and using these to relativise defeasible subsumption. This yields a notion of contextualised rational defeasible subsumption, with contexts described by roles. We also provide a semantic construction for rational closure and a method for its computation, and present a correspondence result between the two.
@article{246,
author = {Katarina Britz, Ivan Varzinczak},
title = {Contextual rational closure for defeasible ALC},
abstract = {Description logics have been extended in a number of ways to support defeasible reason- ing in the KLM tradition. Such features include preferential or rational defeasible concept inclusion, and defeasible roles in complex concept descriptions. Semantically, defeasible subsumption is obtained by means of a preference order on objects, while defeasible roles are obtained by adding a preference order to role interpretations. In this paper, we address an important limitation in defeasible extensions of description logics, namely the restriction in the semantics of defeasible concept inclusion to a single preference order on objects. We do this by inducing a modular preference order on objects from each modular preference order on roles, and using these to relativise defeasible subsumption. This yields a notion of contextualised rational defeasible subsumption, with contexts described by roles. We also provide a semantic construction for rational closure and a method for its computation, and present a correspondence result between the two.},
year = {2019},
journal = {Annals of Mathematics and Artificial Intelligence},
volume = {87},
pages = {83-108},
issue = {1-2},
isbn = {ISSN: 1012-2443},
url = {https://link.springer.com/article/10.1007/s10472-019-09658-2},
doi = {10.1007/s10472-019-09658-2},
}
Britz K, Casini G, Meyer T, Varzinczak I. A KLM Perspective on Defeasible Reasoning for Description Logics. In: Description Logic, Theory Combination, and All That. Switzerland: Springer; 2019. doi:https://doi.org/10.1007/978-3-030-22102-7 _ 7.
In this paper we present an approach to defeasible reasoning for the description logic ALC. The results discussed here are based on work done by Kraus, Lehmann and Magidor (KLM) on defeasible conditionals in the propositional case. We consider versions of a preferential semantics for two forms of defeasible subsumption, and link these semantic constructions formally to KLM-style syntactic properties via representation results. In addition to showing that the semantics is appropriate, these results pave the way for more effective decision procedures for defeasible reasoning in description logics. With the semantics of the defeasible version of ALC in place, we turn to the investigation of an appropriate form of defeasible entailment for this enriched version of ALC. This investigation includes an algorithm for the computation of a form of defeasible entailment known as rational closure in the propositional case. Importantly, the algorithm relies completely on classical entailment checks and shows that the computational complexity of reasoning over defeasible ontologies is no worse than that of the underlying classical ALC. Before concluding, we take a brief tour of some existing work on defeasible extensions of ALC that go beyond defeasible subsumption.
@inbook{240,
author = {Katarina Britz, Giovanni Casini, Thomas Meyer, Ivan Varzinczak},
title = {A KLM Perspective on Defeasible Reasoning for Description Logics},
abstract = {In this paper we present an approach to defeasible reasoning for the description logic ALC. The results discussed here are based on work done by Kraus, Lehmann and Magidor (KLM) on defeasible conditionals in the propositional case. We consider versions of a preferential semantics for two forms of defeasible subsumption, and link these semantic constructions formally to KLM-style syntactic properties via representation results. In addition to showing that the semantics is appropriate, these results pave the way for more effective decision procedures for defeasible reasoning in description logics. With the semantics of the defeasible version of ALC in place, we turn to the investigation of an appropriate form of defeasible entailment for this enriched version of ALC. This investigation includes an algorithm for the computation of a form of defeasible entailment known as rational closure in the propositional case. Importantly, the algorithm relies completely on classical entailment checks and shows that the computational complexity of reasoning over defeasible ontologies is no worse than that of the underlying classical ALC. Before concluding, we take a brief tour of some existing work on defeasible extensions of ALC that go beyond defeasible subsumption.},
year = {2019},
journal = {Description Logic, Theory Combination, and All That},
pages = {147–173},
publisher = {Springer},
address = {Switzerland},
isbn = {978-3-030-22101-0},
url = {https://link.springer.com/book/10.1007%2F978-3-030-22102-7},
doi = {https://doi.org/10.1007/978-3-030-22102-7 _ 7},
}
Casini G, Meyer T, Varzinczak I. Taking Defeasible Entailment Beyond Rational Closure. In: European Conference on Logics in Artificial Intelligence. Switzerland: Springer; 2019. doi:https://doi.org/10.1007/978-3-030-19570-0 _ 12.
We present a systematic approach for extending the KLM framework for defeasible entailment. We first present a class of basic defeasible entailment relations, characterise it in three distinct ways and provide a high-level algorithm for computing it. This framework is then refined, with the refined version being characterised in a similar manner. We show that the two well-known forms of defeasible entailment, rational closure and lexicographic closure, fall within our refined framework, that rational closure is the most conservative of the defeasible entailment relations within the framework (with respect to subset inclusion), but that there are forms of defeasible entailment within our framework that are more “adventurous” than lexicographic closure.
@{238,
author = {Giovanni Casini, Thomas Meyer, Ivan Varzinczak},
title = {Taking Defeasible Entailment Beyond Rational Closure},
abstract = {We present a systematic approach for extending the KLM framework for defeasible entailment. We first present a class of basic defeasible entailment relations, characterise it in three distinct ways and provide a high-level algorithm for computing it. This framework is then refined, with the refined version being characterised in a similar manner. We show that the two well-known forms of defeasible entailment, rational closure and lexicographic closure, fall within our refined framework, that rational closure is the most conservative of the defeasible entailment relations within the framework (with respect to subset inclusion), but that there are forms of defeasible entailment within our framework that are more “adventurous” than lexicographic closure.},
year = {2019},
journal = {European Conference on Logics in Artificial Intelligence},
pages = {182 - 197},
month = {07/05 - 11/05},
publisher = {Springer},
address = {Switzerland},
isbn = {978-3-030-19569-4},
url = {https://link.springer.com/chapter/10.1007%2F978-3-030-19570-0_12},
doi = {https://doi.org/10.1007/978-3-030-19570-0 _ 12},
}
More Info
Latest Research Publications:
Venter AEW, Theunissen MW, Davel MH. Pre-interpolation loss behavior in neural networks. In: Southern African Conference for Artificial Intelligence Research. South Africa: Springer; 2020. doi:https://doi.org/10.1007/978-3-030-66151-9_19.
When training neural networks as classifiers, it is common to observe an increase in average test loss while still maintaining or improving the overall classification accuracy on the same dataset. In spite of the ubiquity of this phenomenon, it has not been well studied and is often dismissively attributed to an increase in borderline correct classifications. We present an empirical investigation that shows how this phenomenon is actually a result of the differential manner by which test samples are processed. In essence: test loss does not increase overall, but only for a small minority of samples. Large representational capacities allow losses to decrease for the vast majority of test samples at the cost of extreme increases for others. This effect seems to be mainly caused by increased parameter values relating to the correctly processed sample features. Our findings contribute to the practical understanding of a common behaviour of deep neural networks. We also discuss the implications of this work for network optimisation and generalisation.
@{401,
author = {Arthur Venter, Marthinus Theunissen, Marelie Davel},
title = {Pre-interpolation loss behavior in neural networks},
abstract = {When training neural networks as classifiers, it is common to observe an increase in average test loss while still maintaining or improving the overall classification accuracy on the same dataset. In spite of the ubiquity of this phenomenon, it has not been well studied and is often dismissively attributed to an increase in borderline correct classifications. We present an empirical investigation that shows how this phenomenon is actually a result of the differential manner by which test samples are processed. In essence: test loss does not increase overall, but only for a small minority of samples. Large representational capacities allow losses to decrease for the vast majority of test samples at the cost of extreme increases for others. This effect seems to be mainly caused by increased parameter values relating to the correctly processed sample features. Our findings contribute to the practical understanding of a common behaviour of deep neural networks. We also discuss the implications of this work for network optimisation and generalisation.},
year = {2020},
journal = {Southern African Conference for Artificial Intelligence Research},
pages = {296-309},
month = {22/02/2021 - 26/02/2021},
publisher = {Springer},
address = {South Africa},
isbn = {978-3-030-66151-9},
doi = {https://doi.org/10.1007/978-3-030-66151-9_19},
}
Research Groups:
More Info
Tezira is Pursuing her PhD in the Adaptive and Cognitive Systems Lab at the University of Cape Town. Her research is on Designing and Evaluating an Agent-based Architecture for Automatic Knowledge Discovery and Evolution. She is also an Assistant Lecturer at Mbarara University of Science and Technology in the Department of Computer Science, Faculty of Computing and Informatics.
Latest Research Publications:
Wanyana T, Moodley D, Meyer T. An Ontology for Supporting Knowledge Discovery and Evolution. In: Proceedings of the First Southern African Conference for Artificial Intelligence Research. SACAIR 2020; 2020.
Knowledge Discovery and Evolution (KDE) is of interest to a broad array of researchers from both Philosophy of Science (PoS) and Artificial Intelligence (AI), in particular, Knowledge Representation and Reasoning (KR), Machine Learning and Data Mining (ML-DM) and the Agent Based Systems (ABS) communities. In PoS, Haig recently pro- posed a so-called broad theory of scientific method that uses abduction for generating theories to explain phenomena. He refers to this method of scientific inquiry as the Abductive Theory of Method (ATOM). In this paper, we analyse ATOM, align it with KR and ML-DM perspectives and propose an algorithm and an ontology for supporting agent based knowledge discovery and evolution based on ATOM. We illustrate the use of the algorithm and the ontology on a use case application for electricity consumption behaviour in residential households.
@inbook{390,
author = {Tezira Wanyana, Deshen Moodley, Thomas Meyer},
title = {An Ontology for Supporting Knowledge Discovery and Evolution},
abstract = {Knowledge Discovery and Evolution (KDE) is of interest to a broad array of researchers from both Philosophy of Science (PoS) and Artificial Intelligence (AI), in particular, Knowledge Representation and Reasoning (KR), Machine Learning and Data Mining (ML-DM) and the Agent Based Systems (ABS) communities. In PoS, Haig recently pro- posed a so-called broad theory of scientific method that uses abduction for generating theories to explain phenomena. He refers to this method of scientific inquiry as the Abductive Theory of Method (ATOM). In this paper, we analyse ATOM, align it with KR and ML-DM perspectives and propose an algorithm and an ontology for supporting agent based knowledge discovery and evolution based on ATOM. We illustrate the use of the algorithm and the ontology on a use case application for electricity consumption behaviour in residential households.},
year = {2020},
journal = {Proceedings of the First Southern African Conference for Artificial Intelligence Research},
pages = {206-221},
publisher = {SACAIR 2020},
isbn = {978-0-620-89373-2(e-book)},
}
More Info
DEGREES LINKED TO THIS GROUP:
2019-Current PhD (Humanities): 'A Critical Inquiry into the Metaphysics for Mind Uploading'.
2019-Current PhD (Humanities): 'A Critical Inquiry into the Metaphysics for Mind Uploading'.
Latest Research Publications:
No Results
Research Groups:
More Info
Latest Research Publications:
Daykin JW, Groult R, Guesnet Y, et al. Efficient pattern matching in degenerate strings with the Burrows–Wheeler transform. Information Processing Letters. 2019;147. doi:https://doi.org/10.1016/j.ipl.2019.03.003.
A degenerate or indeterminate string on an alphabet SIGMA is a sequence of non-empty subsets of SIGMA . Given a degenerate string t of length n and its Burrows–Wheeler transform we present a new method for searching for a degenerate pattern of length m in t running in O ( mn ) time on a constant size alphabet SIGMA. Furthermore, it is a hybrid pattern matching technique that works on both regular and degenerate strings. A degenerate string is said to be conservative if its number of non-solid letters is upper-bounded by a fixed positive constant q; in this case we show that the search time complexity is O ( qm^2 ) for counting
the number of occurrences and O ( qm^2 + occ ) for reporting the found occurrences where occ is the number of occurrences of the pattern in t. Experimental results show that our method performs well in practice.
@article{265,
author = {J.W. Daykin, R. Groult, Y. Guesnet, T. Lecroq, A. Lefebvre, M. Leonard, L. Mouchard, E. Prieur-Gaston, Bruce Watson},
title = {Efficient pattern matching in degenerate strings with the Burrows–Wheeler transform},
abstract = {A degenerate or indeterminate string on an alphabet SIGMA is a sequence of non-empty subsets of SIGMA . Given a degenerate string t of length n and its Burrows–Wheeler transform we present a new method for searching for a degenerate pattern of length m in t running in O ( mn ) time on a constant size alphabet SIGMA. Furthermore, it is a hybrid pattern matching technique that works on both regular and degenerate strings. A degenerate string is said to be conservative if its number of non-solid letters is upper-bounded by a fixed positive constant q; in this case we show that the search time complexity is O ( qm^2 ) for counting
the number of occurrences and O ( qm^2 + occ ) for reporting the found occurrences where occ is the number of occurrences of the pattern in t. Experimental results show that our method performs well in practice.},
year = {2019},
journal = {Information Processing Letters},
volume = {147},
pages = {82 - 87},
publisher = {Elsevier},
doi = {https://doi.org/10.1016/j.ipl.2019.03.003},
}
Runge T, Schaefer I, Knuppel A, Cleophas LGWA, Kourie DG, Watson B. Tool Support for Confidentiality-by-Construction. Ada User Journal . 2019;38(2). doi:https://doi.org/10.1145/3375408.3375413.
In many software applications, it is necessary to preserve confidentiality of information. Therefore, security mechanisms are needed to enforce that secret information does not leak to unauthorized users. However, most language-based techniques that enable in- formation flow control work post-hoc, deciding whether a specific program violates a confidentiality policy. In contrast, we proposed in previous work a refinement-based approach to derive programs that preserve confidentiality-by-construction. This approach follows the principles of Dijkstra’s correctness-by-construction. In this extended abstract, we present the implementation and tool support of that refinement-based approach allowing to specify the information flow policies first and to create programs in a simple while language which comply to these policies by construction. In particular, we present the idea of confidentiality-by-construction using an example and discuss the IDE C-CorC supporting this development approach.
@article{263,
author = {T. Runge, I. Schaefer, A. Knuppel, L.G.W.A. Cleophas, D.G Kourie, Bruce Watson},
title = {Tool Support for Confidentiality-by-Construction},
abstract = {In many software applications, it is necessary to preserve confidentiality of information. Therefore, security mechanisms are needed to enforce that secret information does not leak to unauthorized users. However, most language-based techniques that enable in- formation flow control work post-hoc, deciding whether a specific program violates a confidentiality policy. In contrast, we proposed in previous work a refinement-based approach to derive programs that preserve confidentiality-by-construction. This approach follows the principles of Dijkstra’s correctness-by-construction. In this extended abstract, we present the implementation and tool support of that refinement-based approach allowing to specify the information flow policies first and to create programs in a simple while language which comply to these policies by construction. In particular, we present the idea of confidentiality-by-construction using an example and discuss the IDE C-CorC supporting this development approach.},
year = {2019},
journal = {Ada User Journal},
volume = {38},
pages = {64 - 68},
issue = {2},
doi = {https://doi.org/10.1145/3375408.3375413},
}
Runge T, Schaefer I, Cleophas LGWA, Thum T, Kourie DG, Watson B. Tool Support for Correctness-by-Construction. In: European Joint Conferences on Theory and Practice of Software (ETAPS). Switzerland: Springer; 2019. doi:https://doi.org/10.1007/978-3-030-16722-6 _ 2.
Correctness-by-Construction (CbC) is an approach to incrementally create formally correct programs guided by pre- and postcondition specifications. A program is created using refinement rules that guarantee the resulting implementation is correct with respect to the specification. Although CbC is supposed to lead to code with a low defect rate, it is not prevalent, especially because appropriate tool support is missing. To promote CbC, we provide tool support for CbC-based program development. We present CorC, a graphical and textual IDE to create programs in a simple while-language following the CbC approach. Starting with a specification, our open source tool supports CbC developers in refining a program by a sequence of refinement steps and in verifying the correctness of these refinement steps using the theorem prover KeY. We evaluated the tool with a set of standard examples on CbC where we reveal errors in the provided specification. The evaluation shows that our tool reduces the verification time in comparison to post-hoc verification.
@{262,
author = {T. Runge, I. Schaefer, L.G.W.A. Cleophas, T. Thum, D.G Kourie, Bruce Watson},
title = {Tool Support for Correctness-by-Construction},
abstract = {Correctness-by-Construction (CbC) is an approach to incrementally create formally correct programs guided by pre- and postcondition specifications. A program is created using refinement rules that guarantee the resulting implementation is correct with respect to the specification. Although CbC is supposed to lead to code with a low defect rate, it is not prevalent, especially because appropriate tool support is missing. To promote CbC, we provide tool support for CbC-based program development. We present CorC, a graphical and textual IDE to create programs in a simple while-language following the CbC approach. Starting with a specification, our open source tool supports CbC developers in refining a program by a sequence of refinement steps and in verifying the correctness of these refinement steps using the theorem prover KeY. We evaluated the tool with a set of standard examples on CbC where we reveal errors in the provided specification. The evaluation shows that our tool reduces the verification time in comparison to post-hoc verification.},
year = {2019},
journal = {European Joint Conferences on Theory and Practice of Software (ETAPS)},
pages = {25 - 42},
month = {06/04 - 11/04},
publisher = {Springer},
address = {Switzerland},
isbn = {78-3-030-16721-9},
url = {https://link.springer.com/content/pdf/10.1007/978-3-030-16722-6.pdf},
doi = {https://doi.org/10.1007/978-3-030-16722-6 _ 2},
}
Watson B. The impact of using a contract-driven, test-interceptor based software development approach. In: Annual conference of The South African Institute of Computer Scientists and Information Technologists (SAICSIT 2018). New York: ACM; 2018. https://doi.org/10.475/123_4.
A contract-driven development approach requires the formalization of component requirements in the form of a component contract. The Use Case, Responsibility Driven Analysis and Design (URDAD) methodology is based on the contract-driven development approach and uses contracts to capture user requirements and perform a technology-neutral design across layers of granularity. This is achieved by taking use-case based functional requirements through an iterative design process and generating various levels of granularity iteratively.
In this project, the component contracts that were captured by utilizing the URDAD approach are used to generate test interceptors which validate whether, in the context of rendering component services, the component contracts are satisfied. To achieve this, Java classes and interfaces are annotated with pre- and postconditions to represent the contracts in code. Annotation processors are then used to automatically generate test-interceptor classes by processing the annotations. The test-interceptor classes encapsulate test-logic and are interface-compatible with their underlying component counterparts. This enable test-interceptors to intercept service requests to the underlying counterpart components in order to verify contract adherence. The generated test interceptors can be used for unit testing as well as real-time component monitoring. This development approach, utilized within the URDAD methodology would then result in unit and integration tests across levels of granularity.
Empirical data from actual software development projects will be used to assess the impact of introducing such a development approach in real software development projects. In particular, the study assesses the impact on the quality attributes of the software development process, as well as the qualities of the software produced by the process.
Process qualities measured include development productivity (the rate at which software is produced), correctness (the rate at which the produced software meets the clients requirements) and the certifiability of the software development process (which certifiability requirements are fully or partially addressed by the URDAD development approach). Software qualities measured include reusability (empirical and qualitative), simplicity (the inverse of the complexity measure) and bug density (number of defects in a module).
The study aims to show conclusively how the approach impacts the creation of correct software which meets the client requirements, how productivity is affected and if the approach enhances or hinders certifiability. The study also aims to determine if testinterceptors
are a viable mechanism to produce high-quality tests that contribute to the creation of correct software. Furthermore, the study aims to determine if the software produced by applying this approach yield improved reusability or not, if the software becomes
more or less complex and if more or less bugs are induced.
@{211,
author = {Bruce Watson},
title = {The impact of using a contract-driven, test-interceptor based software development approach},
abstract = {A contract-driven development approach requires the formalization of component requirements in the form of a component contract. The Use Case, Responsibility Driven Analysis and Design (URDAD) methodology is based on the contract-driven development approach and uses contracts to capture user requirements and perform a technology-neutral design across layers of granularity. This is achieved by taking use-case based functional requirements through an iterative design process and generating various levels of granularity iteratively.
In this project, the component contracts that were captured by utilizing the URDAD approach are used to generate test interceptors which validate whether, in the context of rendering component services, the component contracts are satisfied. To achieve this, Java classes and interfaces are annotated with pre- and postconditions to represent the contracts in code. Annotation processors are then used to automatically generate test-interceptor classes by processing the annotations. The test-interceptor classes encapsulate test-logic and are interface-compatible with their underlying component counterparts. This enable test-interceptors to intercept service requests to the underlying counterpart components in order to verify contract adherence. The generated test interceptors can be used for unit testing as well as real-time component monitoring. This development approach, utilized within the URDAD methodology would then result in unit and integration tests across levels of granularity.
Empirical data from actual software development projects will be used to assess the impact of introducing such a development approach in real software development projects. In particular, the study assesses the impact on the quality attributes of the software development process, as well as the qualities of the software produced by the process.
Process qualities measured include development productivity (the rate at which software is produced), correctness (the rate at which the produced software meets the clients requirements) and the certifiability of the software development process (which certifiability requirements are fully or partially addressed by the URDAD development approach). Software qualities measured include reusability (empirical and qualitative), simplicity (the inverse of the complexity measure) and bug density (number of defects in a module).
The study aims to show conclusively how the approach impacts the creation of correct software which meets the client requirements, how productivity is affected and if the approach enhances or hinders certifiability. The study also aims to determine if testinterceptors
are a viable mechanism to produce high-quality tests that contribute to the creation of correct software. Furthermore, the study aims to determine if the software produced by applying this approach yield improved reusability or not, if the software becomes
more or less complex and if more or less bugs are induced.},
year = {2018},
journal = {Annual conference of The South African Institute of Computer Scientists and Information Technologists (SAICSIT 2018)},
pages = {322-326},
month = {26/09-28/09},
publisher = {ACM},
address = {New York},
isbn = {123-4567-24-567/08/06},
url = {https://doi.org/10.475/123_4},
}
Watson B. Three Strategies for the Dead-Zone String Matching Algorithm. In: The Prague Stringology Conference. Prague, Czech Republic: Prague Stringology Club; 2018. http://www.stringology.org/.
No Abstract
@{210,
author = {Bruce Watson},
title = {Three Strategies for the Dead-Zone String Matching Algorithm},
abstract = {No Abstract},
year = {2018},
journal = {The Prague Stringology Conference},
pages = {117-128},
month = {27/08-28/08},
publisher = {Prague Stringology Club},
address = {Prague, Czech Republic},
isbn = {978-80-01-06484-9},
url = {http://www.stringology.org/},
}
