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See detailA Dynamic Approach for Combining Abstract Argumentation Semantics – Technical Report
Dauphin, Jérémie UL; Cramer, Marcos UL; van der Torre, Leon UL

Report (2018)

Abstract argumentation semantics provide a direct relation from an argumentation framework to corresponding sets of acceptable arguments, or equivalently to labeling functions. Instead, we study step-wise ... [more ▼]

Abstract argumentation semantics provide a direct relation from an argumentation framework to corresponding sets of acceptable arguments, or equivalently to labeling functions. Instead, we study step-wise update relations on argumentation frameworks whose fixpoints represent the labeling functions on the arguments. We make use of this dynamic approach in order to study novel ways of combining abstract argumentation semantics. In particular, we introduce the notion of a merge of two argumentation semantics, which is defined in such a way that the merge of the preferred and the grounded semantics is the complete semantics. Finally we consider how to define new semantics using the merge operator, in particular how meaningfully combine features of naive-based and complete-based semantics. [less ▲]

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See detailProceedings - 2017 ILILAS Distinguished Lectures
Bouvry, Pascal UL; Bisdorff, Raymond; Schommer, Christoph UL et al

Report (2018)

The Proceedings summarizes the 12 lectures that have taken place within the ILIAS Dinstguished Lecture series 2017. It contains a brief abstract of the talks as well as some additional information about ... [more ▼]

The Proceedings summarizes the 12 lectures that have taken place within the ILIAS Dinstguished Lecture series 2017. It contains a brief abstract of the talks as well as some additional information about each speaker. [less ▲]

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See detailPreference in Abstract Argumentation
Kaci, Souhila; van der Torre, Leon UL; Villata, Serena

in Computational Models of Argument (2018)

Consider an argument A that is attacked by an argument B, while A is preferred to B. Existing approaches will either ignore the attack or reverse it. In this paper we introduce a new reduction of ... [more ▼]

Consider an argument A that is attacked by an argument B, while A is preferred to B. Existing approaches will either ignore the attack or reverse it. In this paper we introduce a new reduction of preference and attack to defeat, based on the idea that in such a case, instead of ignoring the attack, the preference is ignored. We compare this new reduction with the two existing ones using a principle-based approach, for the four Dung semantics. The principle-based or axiomatic approach is a methodology to choose an argumentation semantics for a particular application, and to guide the search for new argumentation semantics. For this analysis, we also introduce a fourth reduction, and a semantics for preference-based argumentation based on extension selection. Our classification of twenty alternatives for preference-based abstract argumentation semantics using six principles suggests that our new reduction has some advantages over the existing ones, in the sense that if the set of preferences increases, the sets of accepted arguments increase as well. [less ▲]

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See detailPresent and Future of Formal Argumentation (Dagstuhl Perspectives Workshop 15362)
Gabbay, Dov UL; Giacomin, Massimiliano; Liao, Beishui UL et al

in Dagstuhl Manifestos (2018), 7(1), 69--95

Formal Argumentation is emerging as a key reasoning paradigm building bridges among knowledge representation and reasoning in artificial intelligence, informal argumentation in philosophy and linguistics ... [more ▼]

Formal Argumentation is emerging as a key reasoning paradigm building bridges among knowledge representation and reasoning in artificial intelligence, informal argumentation in philosophy and linguistics, legal and ethical argumentation, mathematical and logical reasoning, and graph-theoretic reasoning. It aims to capture diverse kinds of reasoning and dialogue activities in the presence of uncertainty and conflicting information in a formal and intuitive way, with potential applications ranging from argumentation mining, via LegalTech and machine ethics, to therapy in clinical psychology. The turning point for the modern stage of formal argumentation theory, much similar to the introduction of possible worlds semantics for the theory of modality, is the framework and language of Dung’s abstract argumentation theory introduced in 1995. This means that nothing could remain the same as before 1995 — it should be a focal point of reference for any study of argumentation, even if it is critical about it. Now, in modal logic, the introduction of the possible worlds semantics has led to a complete paradigm shift, both in tools and new subjects of studies. This is still not fully true for what is going on in argumentation theory. The Dagstuhl workshop led to the first volume of a handbook series in formal argumentation, reflecting the new stage of the development of argumentation theory. [less ▲]

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See detailEthics by Design: Necessity or Curse?
Dignum, Virginia; Baldoni, Matteo; Baroglio, Cristina et al

in Proceedings of the 2018 AAAI/ACM Conference on AI, Ethics, and Society AIES 2018, New Orleans, LA, USA, February 02-03, 2018 (2018)

Ethics by Design concerns the methods, algorithms and tools needed to endow autonomous agents with the capability to reason about the ethical aspects of their decisions, and the methods, tools and ... [more ▼]

Ethics by Design concerns the methods, algorithms and tools needed to endow autonomous agents with the capability to reason about the ethical aspects of their decisions, and the methods, tools and formalisms to guarantee that an agent's behavior remains within given moral bounds. In this context some questions arise: How and to what extent can agents understand the social reality in which they operate, and the other intelligences (AI, animals and humans) with which they co-exist? What are the ethical concerns in the emerging new forms of society, and how do we ensure the human dimension is upheld in interactions and decisions by autonomous agents?. But overall, the central question is: "Can we, and should we, build ethically-aware agents?" This paper presents initial conclusions from the thematic day of the same name held at PRIMA2017, on October 2017. [less ▲]

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See detailBuilding Jiminy Cricket: An Architecture for Moral Agreements Among Stakeholders
Liao, Beishui; Slavkovik, Marija; van der Torre, Leon UL

in AAAI/ACM Artificial Intelligence, Ethics and Society (2018)

An autonomous system is constructed by a manufacturer, operates in a society subject to norms and laws, and is interacting with end-users. We address the challenge of how the moral values and views of all ... [more ▼]

An autonomous system is constructed by a manufacturer, operates in a society subject to norms and laws, and is interacting with end-users. We address the challenge of how the moral values and views of all stakeholders can be integrated and reflected in the moral behaviour of the autonomous system. We propose an artificial moral agent architecture that uses techniques from normative systems and formal argumentation to reach moral agreements among stakeholders. We show how our architecture can be used not only for ethical practical reasoning and collaborative decision-making, but also for the explanation of such moral behavior. [less ▲]

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See detailArguing about constitutive and regulative norms
Pigozzi, Gabriella; van der Torre, Leon UL

in Journal of Applied Non-Classical Logics (2018), 28(2-3), 189--217

Formal arguments are often represented by (support, conclusion) pairs, but in this paper we consider normative arguments represented by sequences of (brute, institutional, deontic) triples, where ... [more ▼]

Formal arguments are often represented by (support, conclusion) pairs, but in this paper we consider normative arguments represented by sequences of (brute, institutional, deontic) triples, where constitutive norms derive institutional facts from brute facts, and regulative norms derive deontic facts like obligations and permissions from institutional facts. The institutional facts may be seen as the reasons explaining or warranting the deontic obligations and permissions, and therefore they can be attacked by other normative arguments too. We represent different aspects of normative reasoning by different kinds of consistency checks among these triples, and we use formal argumentation theory to resolve conflicts among such normative arguments. In particular, we introduce various requirements for arguing about norms concerning violations, contrary-to-duty obligations, dilemmas, conflict resolution and different kinds of norms, and we introduce a formal argumentation theory satisfying the requirements. In order to illustrate our framework, we introduce a running example based on university regulations for prospective and actual students. [less ▲]

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See detailMore Attention and Less Repetitive and Stereotyped Behaviors using a Robot with Children with Autism
Pinto Costa, Andreia UL; Charpiot, Louise UL; Rodriguez Lera, Francisco Javier UL et al

in 27th IEEE International Symposium on Robot and Human Interactive Communication, RO-MAN 2018, Nanjing, China, August 27-31, 2018 (2018)

The aim of the present study was to assess the usefulness of QTrobot, a socially assistive robot, in interventions with children with autism spectrum disorder (ASD) by assessing children's attention ... [more ▼]

The aim of the present study was to assess the usefulness of QTrobot, a socially assistive robot, in interventions with children with autism spectrum disorder (ASD) by assessing children's attention, imitation, and presence of repetitive and stereotyped behaviors. Fifteen children diagnosed with ASD, aged from 4 to 14 years participated in two short interactions, one with a person and one with the robot. Statistical analyses revealed that children directed more attention towards the robot than towards the person, imitated the robot as much as the person, and engaged in fewer repetitive or stereotyped behaviors with the robot than with the person. These results support previous research demonstrating the usefulness of robots in short interactions with children with ASD and provide new evidence to the usefulness of robots in reducing repetitive and stereotyped behaviors in children with ASD, which can affect children's learning. [less ▲]

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See detailFrom Georeferenced Data to Socio-Spatial Knowledge. Ontology Design Patterns to Discover Domain-Specific Knowledge from Crowdsourced Data
Calafiore, Alessia; Boella, Guido; van der Torre, Leon UL

in 21st International Conference on Knowledge Engineering and Knowledge Management (2018)

So far, ontologies developed to support Geographic Information science have been mostly designed from a space-centered rather than a human-centered and social perspective. In the last decades, a wealth of ... [more ▼]

So far, ontologies developed to support Geographic Information science have been mostly designed from a space-centered rather than a human-centered and social perspective. In the last decades, a wealth of georeferenced data is collected through sensors, mobile and web platforms from the crowd, providing rich information about people’s collective experiences and behaviors in cities. As a consequence, these new data sources require models able to make machine-understandable the social meanings and uses people commonly associate with certain places. This contribution proposes a set of reusable Ontology Design Patterns (ODP) to guide a data mining workflow and to semantically enrich the mined results. The ODPs explicitly aim at representing two facets of the geographic knowledge - the built environment and people social behavior in cities - as well as the way they interact. Modelling the interplay between the physical and the human aspects of the urban environment provides an ontology representation of the socio-spatial knowledge which can be used as baseline domain knowledge for analysing and interpreting georeferenced data collected through crowdsourcing. An experimentation using a TripAdvisor data sample to recognize food consumption practices in the city of Turin is presented. [less ▲]

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See detailInput/output logics with a consistency check
Parent, Xavier UL; van der Torre, Leon UL

in Pigozzi, Gabriella; Broersen, Jan; Condoravdi, Cleo (Eds.) et al Deontic Logic and Normative Systems (DEON 2018) (2018)

Norm-based semantics to deontic logic typically come in an unconstrained and constrained version, where the unconstrained version comes with a proof system, and the constraints handle phenomena such as ... [more ▼]

Norm-based semantics to deontic logic typically come in an unconstrained and constrained version, where the unconstrained version comes with a proof system, and the constraints handle phenomena such as dilemmas, contrary-to-duty reasoning, uncertaintyanddefeasibility. Thisisanalogoustotheuseofrule-basedlanguagesin non-monotonic logic such as logic programming or default logic, but in contrast to the traditional modal framework. Traditionally, for example, specific modal deontic logics have been defined that make dilemmas inconsistent, as well as other modal deontic logics representing dilemmas in a consistent way. This issue was raised recently in the input/output logic framework, and weaker unconstrained logics have been defined handling phenomena like dilemmas and contrary-to-duty reasoning. In this paper we introduce a semantics and proof theory for a system with various desirable properties. We show that our new deontic logic satisfies a criterion posed several years ago by Broersen and van der Torre, allowing deontic detachment while preventing Prakken and Sergot’s pragmatic oddities as well as Sergot’s drowning problem. [less ▲]

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See detailProbabilistic Abstract Argumentation Based on SCC Decomposability
Rienstra, Tjitze; Thimm, Matthias; Liao, Beishui UL et al

in Principles of Knowledge Representation and Reasoning: Proceedings of the Sixteenth International Conference, KR 2018, Tempe, Arizona 30 October - 2 November 2018. (2018)

In this paper we introduce a new set of general principles for probabilistic abstract argumentation. The main principle is a probabilistic analogue of SCC decomposability, which ensures that the ... [more ▼]

In this paper we introduce a new set of general principles for probabilistic abstract argumentation. The main principle is a probabilistic analogue of SCC decomposability, which ensures that the probabilistic evaluation of an argumentation framework complies with the probabilistic (in)dependencies implied by the graph topology. We introduce various examples of probabilistic semantics and determine which principles they satisfy. Our work also provides new insights into the relationship between abstract argumentation and the theory of Bayesian networks. [less ▲]

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See detailA Deontic Logic Reasoning Infrastructure
Benzmüller, Christoph UL; Parent, Xavier UL; van der Torre, Leon UL

in Sailing Routes in the World of Computation, 14th Conference on Computability in Europe, CiE 2018, Kiel, Germany, July 30 – August 3, 2018, Proceedings (2018)

A flexible infrastructure for the automation of deontic and normative reasoning is presented. Our motivation is the development, study and provision of legal and moral reasoning competencies in future ... [more ▼]

A flexible infrastructure for the automation of deontic and normative reasoning is presented. Our motivation is the development, study and provision of legal and moral reasoning competencies in future intelligent machines. Since there is no consensus on the “best” deontic logic formalisms and since the answer may be application specific, a flexible infrastructure is proposed in which candidate logic formalisms can be varied, assessed and compared in experimental ethics application studies. Our work thus links the historically rich research areas of classical higher-order logic, deontic logics, normative reasoning and formal ethics. [less ▲]

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See detailAbstract and Concrete Decision Graphs for Choosing Extensions of Argumentation Frameworks - Technical Report
Dauphin, Jérémie UL; Cramer, Marcos UL; van der Torre, Leon UL

Report (2018)

Most argumentation semantics allow for multiple extensions, which raises the question of how to choose among extensions. We propose to study this question as a decision problem. Inspired by decision trees ... [more ▼]

Most argumentation semantics allow for multiple extensions, which raises the question of how to choose among extensions. We propose to study this question as a decision problem. Inspired by decision trees commonly used in economics, we introduce the notion of a decision graph for deciding between the multiple extensions of a given AF in a given semantics. We distinguish between abstract decision graphs and concrete instantiations thereof. Inspired by the principle-based approach to argumentation, we formulate two principles that mappings from argumentation frameworks to decision graphs should satisfy, the principle of decision-graph directionality and the one of directional decision-making. We then propose a concrete instantiation of decision graphs, which satisfies one of these principles. Finally, we discuss the potential for further research based on this novel methodology. [less ▲]

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See detailArgumentation as Exogenous Coordination
van der Torre, Leon UL; Rienstra, Tjitze; Gabbay, Dov UL

in It's All About Coordination (2018)

Formal argumentation is one of the most popular approaches in modern logic and reasoning. The theory of abstract argumentation introduced by Dung in 1995 has shifted the focus from the internal structure ... [more ▼]

Formal argumentation is one of the most popular approaches in modern logic and reasoning. The theory of abstract argumentation introduced by Dung in 1995 has shifted the focus from the internal structure of arguments to relations among arguments, and temporal dynamics for abstract argumentation was proposed by Barringer, Gabbay and Woods in 2005. In this tradition, we see arguments as reasoning processes, and the interaction among them as a coordination process.We argue that abstract argumentation can adopt ideas and techniques from formal theories of coordination, and as an example we propose a model of sequential abstract argumentation loosely inspired by Reo’s model of exogenous coordination. We show how the argumentation model can represent the temporal dynamics of the liar paradox and predator-prey like behaviour. [less ▲]

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See detailPrioritized norms in formal argumentation
Liao, Beishui; Oren, Nir; van der Torre, Leon UL et al

in Journal of Logic and Computation (2018)

To resolve conflicts amongst norms, various non-monotonic formalisms can be used to perform prioritized normative reasoning. Meanwhile, formal argumentation provides a way to represent non-monotonic ... [more ▼]

To resolve conflicts amongst norms, various non-monotonic formalisms can be used to perform prioritized normative reasoning. Meanwhile, formal argumentation provides a way to represent non-monotonic logics. In this paper we propose a representation of prioritized normative reasoning by argumentation. Using hierarchical abstract normative systems (HANS), we define three kinds of prioritized normative reasoning approaches called Greedy, Reduction and Optimization. Then, after formulating an argumentation theory for a HANS, we show that for a totally ordered HANS, Greedy and Reduction can be represented in argumentation by applying the weakest link and the last link principles, respectively, and Optimization can be represented by introducing additional defeats capturing the idea that for each argument that contains a norm not belonging to the maximal obeyable set then this argument should be rejected. [less ▲]

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See detailAbstract and Concrete Decision Graphs for Choosing Extensions of Argumentation Frameworks
Dauphin, Jérémie UL; Cramer, Marcos UL; van der Torre, Leon UL

in Computational Models of Argument (2018)

Most argumentation semantics allow for multiple extensions, which raises the question of how to choose among extensions. We propose to study this question as a decision problem. Inspired by decision trees ... [more ▼]

Most argumentation semantics allow for multiple extensions, which raises the question of how to choose among extensions. We propose to study this question as a decision problem. Inspired by decision trees commonly used in economics, we introduce the notion of a decision graph for deciding between the multiple extensions of a given AF in a given semantics. We distinguish between abstract decision graphs and concrete instantiations thereof. Inspired by the principle-based approach to argumentation, we formulate two principles that mappings from argumentation frameworks to decision graphs should satisfy, the principles of decision-graph directionality and that of directional decision-making. We then propose a concrete instantiation of decision graphs, which satisfies one of these principles. Finally, we discuss the potential for further research based on this novel methodology. [less ▲]

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See detailRepresentation Equivalences among Argumentation Frameworks
Liao, Beishui; van der Torre, Leon UL

in Computational Models of Argument (2018)

In Dung’s abstract argumentation theory, an extension can be represented by subsets of it in the sense that from each of these subsets, the extension can be obtained again by iteratively applying the ... [more ▼]

In Dung’s abstract argumentation theory, an extension can be represented by subsets of it in the sense that from each of these subsets, the extension can be obtained again by iteratively applying the characteristic function. Such so-called regular representations can be used to differentiate argumentation frameworks having the same extensions. In this paper we provide a full characterization of relations between seven different types of representation equivalence. [less ▲]

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See detailMultiagent Deontic Logic and its Challenges from a Normative Systems Perspective
Pigozzi, Gabriella; van der Torre, Leon UL

in IfCoLog Journal of Logics and Their Applications (2017)

This article gives an overview of several challenges studied in deontic logic, with an emphasis on challenges involving agents. We start with traditional modal deontic logic using preferences to address ... [more ▼]

This article gives an overview of several challenges studied in deontic logic, with an emphasis on challenges involving agents. We start with traditional modal deontic logic using preferences to address the challenge of contrary-toduty reasoning, and STIT theory addressing the challenges of non-deterministic actions, moral luck and procrastination. Then we turn to alternative normbased deontic logics detaching obligations from norms to address the challenge of Jørgensen’s dilemma, including the question how to derive obligations from a normative system when agents cannot assume that other agents comply with their norms. We discuss also some traditional challenges from the viewpoint of normative systems: when a set of norms may be termed ‘coherent’, how to deal with normative conflicts, how to combine normative systems and traditional deontic logic, how various kinds of permission can be accommodated, how meaning postulates and counts-as conditionals can be taken into account,how sets of norms may be revised and merged, and how normative systems can be combined with game theory. The normative systems perspective means that norms, not ideality or preference, should take the central position in deontic semantics, and that a semantics that represents norms explicitly provides a helpful tool for analysing, clarifying and solving the problems of deontic logic. We focus on the challenges rather than trying to give full coverage of related work, for which we refer to the handbook of deontic logic and normative systems. [less ▲]

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See detailDetachment in Normative Systems: Examples, inference Patterns, Properties
Parent, Xavier UL; van der Torre, Leon UL

in IfCoLog Journal of Logics and Their Applications (2017), 4(9), 2295-3039

There is a variety of ways to reason with normative systems. This partly reflects a variety of semantics developed for deontic logic, such as traditional semantics based on possible worlds, or alternative ... [more ▼]

There is a variety of ways to reason with normative systems. This partly reflects a variety of semantics developed for deontic logic, such as traditional semantics based on possible worlds, or alternative semantics based on algebraic methods, explicit norms or techniques from non-monotonic logic. This diversity raises the question how these reasoning methods are related, and which reasoning method should be chosen for a particular application. In this paper we discuss the use of examples, inference patterns, and more abstract properties. First, benchmark examples can be used to compare ways to reason with normative systems. We give an overview of several benchmark examples of normative reasoning and deontic logic: van Fraassen’s paradox, Forrester’s paradox, Prakken and Sergot’s cottage regulations, Jeffrey’s disarmament example, Chisholm’s paradox, Makinson’s Möbius strip, and Horty’s priority examples. Moreover, we distinguish various interpretations that can be given to these benchmark examples, such as consistent interpretations, dilemma interpretations, and violability interpretations. Second, inference patterns can be used to compare different ways to reason with normative systems. Instead of analysing the benchmark examples semantically, as it is usually done, in this paper we use inference patterns to analyse them at a higher level of abstraction. We discuss inference patterns reflecting typical logical properties such as strengthening of the antecedent or weakening of the consequent. Third, more abstract properties can be defined to compare different ways to reason with normative systems. To define these more abstract properties, we first present a formal framework around the notion of detachment. Some of the ten properties we introduce are derived from the inference patterns, but others are more abstract: factual detachment, violation detection, substitution, replacements of equivalents, implication, para-consistency, conjunction, factual monotony, norm monotony, and norm induction. We consider these ten properties as desirable for a reasoning method for normative systems. [less ▲]

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See detailImplementation of Carmo and Jones Dyadic Deontic Logic in Isabelle/HOL
Benzmüller, Christoph UL; Farjami, Ali UL; Parent, Xavier UL et al

Scientific Conference (2017, July 06)

A shallow semantical embedding of a dyadic deontic logic (by Carmo and Jones) in Isabelle/HOL is presented. First experiments provide evidence that this logic implementation fruitfully enables interactive ... [more ▼]

A shallow semantical embedding of a dyadic deontic logic (by Carmo and Jones) in Isabelle/HOL is presented. First experiments provide evidence that this logic implementation fruitfully enables interactive and automated reasoning at the meta-level the object-level. [less ▲]

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