Leon van der Torre

Leon van der Torre
University of Luxembourg · Computer Science and Communications Research Unit

Full professor

About

500
Publications
88,242
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8,588
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Additional affiliations
January 2006 - present
University of Luxembourg
December 1998 - November 2002
Vrije Universiteit Amsterdam

Publications

Publications (500)
Chapter
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The recent rapid evolution of artificial intelligence and its widespread application in a multitude of domains led to the emergence of new heterogeneous systems where humans cohabit with software agents. The logics needed in these new-generation systems with intelligent behavior (AIs) have to accommodate reasoning about norms and values: these cons...
Chapter
Base argumentation is a logic-based instantiation of abstract argumentation. Each base argument is a subset of the given knowledge base. In this paper, we show that base argumentation satisfies some rationality postulates, and that base argumentation is equivalent to deductive argumentation under complete semantics. Due to its simplicity, base argu...
Chapter
Baumann, Brewka and Ulbricht [3, 4] recently introduced weak admissibility as an alternative to Dung’s notion of admissibility [7], and they used it to define weakly preferred, weakly complete and weakly grounded semantics of argumentation frameworks. In earlier work, we introduced two variants of their new semantics which we called qualified and s...
Preprint
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Artificial Intelligence (AI) logic formalizes the reasoning of intelligent agents. In this paper, we discuss how an argumentation-based AI logic could be used also to formalize important aspects of social reasoning. Besides reasoning about the knowledge and actions of individual agents, social AI logic can reason also about social dependencies amon...
Conference Paper
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agent argumentation frameworks extend Dung’s theory with agents, and in this paper we study four types of semantics for them. First, agent defense semantics replaces Dung’s notion of defense by some kind of agent defense. Second, social agent semantics prefers arguments that belong to more agents. Third, agent reduction semantics considers the pers...
Conference Paper
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In this discussion paper we are interested in anankastic conditionals such as "if you want to smoke you must buy cigarettes" and near-anankastic conditionals such as "if you want to smoke, you must not buy cigarettes." First, we discuss challenges to representing such conditionals in deontic logic, in particular in relation to the use of context. W...
Article
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This article seeks to address the problem of the ‘resource consumption bottleneck’ of creating legal semantic technologies manually. It describes a semantic role labeling based information extraction system to extract definitions and norms from legislation and represent them as structured norms in legal ontologies. The output is intended to help ma...
Chapter
The theory of formal argumentation distinguishes and unifies various notions of attack, support and preference among arguments, and principles are used to classify the semantics of various kinds of argumentation frameworks. In this paper, we consider the case in which we know that an argument is supporting another one, but we do not know yet which...
Article
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The principle-based approach is a methodology to classify and analyse argumentation semantics. In this paper we classify seven of the main alternatives for argumentation semantics using a set of new robustness principles. These principles complement Baroni and Giacomin’s original classification and deal with the behaviour of a semantics when the ar...
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This position paper connects the areas and communities of abstract argumentation and attack-defence trees in the area of security. Both areas deal with attacks, defence and support and both areas rely on applications dealing with human aggressive activities. The unifying idea we use in this paper is to regard arguments as AND-OR attack trees as pro...
Article
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The LogiKEy workbench and dataset for ethical and legal reasoning is presented. This workbench simultaneously supports development, experimentation, assessment and deployment of formal logics and ethical and legal theories at different conceptual layers. More concretely, it comprises, in form of a data set (Isabelle/HOL theory files), formal encodi...
Conference Paper
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Deontic logic is the logic of normative concepts such as obligations, permissions, and rights, and it is used in knowledge representation to formalize ethical and legal reasoning. Norms can be conflicting and subject to exceptions, they can originate from various authorities, and they can specify ideal as well as sub-ideal situations and actions. A...
Preprint
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In the next coming years, space activities are expected to undergo a radical transformation with the emergence of new satellite systems or new services which will incorporate the contributions of artificial intelligence and machine learning defined as covering a wide range of innovations from autonomous objects with their own decision-making power...
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A framework and methodology—termed LogiKEy—for the design and engineering of ethical reasoners, normative theories and deontic logics is presented. The overall motivation is the development of suitable means for the control and governance of intelligent autonomous systems. LogiKEy's unifying formal framework is based on semantical embeddings of deo...
Preprint
Full-text available
A framework and methodology---termed LogiKEy---for the design and engineering of ethical reasoners, normative theories and deontic logics is presented. The overall motivation is the development of suitable means for the control and governance of intelligent autonomous systems. LogiKEy's unifying formal framework is based on semantical embeddings of...
Preprint
In this paper we address the interplay among intention, time, and belief in dynamic environments. The first contribution is a logic for reasoning about intention, time and belief, in which assumptions of intentions are represented by preconditions of intended actions. Intentions and beliefs are coherent as long as these assumptions are not violated...
Article
In this paper we address the interplay among intention, time, and belief in dynamic environments. The first contribution is a logic for reasoning about intention, time and belief, in which assumptions of intentions are represented by preconditions of intended actions. Intentions and beliefs are coherent as long as these assumptions are not violated...
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In this paper we use formal argumentation to design non-monotonic deontic logics, based on two monotonic deontic logics. In particular, we use the structured argumentation theory ASPIC to define non-monotonic variants of well-understood modal logics. We illustrate the approach using argumentation about free-choice permission.
Preprint
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argumentation theory, many argumentation semantics have been proposed for evaluating argumentation frameworks. This paper is based on the following research question: Which semantics corresponds well to what humans consider a rational judgment on the acceptability of arguments? There are two systematic ways to approach this research question: A nor...
Conference Paper
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 behavior of the autonomous system. We propose an artificial moral agent architecture th...
Preprint
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 t...
Conference Paper
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 shor...
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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...
Article
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 institutio...
Conference Paper
Full-text available
The aim of the present study was to assess the usefulness of QT, 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 int...
Chapter
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. I...
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Triple-A is an abstract argumentation model, distinguishing the global argumentation of judges from the local argumentation of accused, prosecutors, witnesses, lawyers, and experts. In Triple-A, agents have partial knowledge of the arguments and attacks of other agents, and they decide autonomously whether to accept or reject their own arguments, a...
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Instead of custom-building a new ontology from scratch, knowledge resources can be elicited, reused and engineered to develop legal ontologies with the goal of promoting the application of good practices and speeding up the ontology development process. This paper focuses on the specificities of non-ontological resources in the legal domain, and pr...
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In this chapter we present an ontology design pattern to conceptualize complaints, an important concept still uncovered by ODPs. The proposed Complaint Ontology Pattern (COP) has been designed based on the analysis of free text complaints from available complaint datasets (banking, air transport, automobile), among other knowledge sources. We prese...
Book
This book constitutes the refereed proceedings of the 20th International Conference on Principles and Practice of Multi-Agent Systems, PRIMA 2017, held in Nice, France, in October/November 2017. The 24 revised full papers presented together with one abstract of a keynote talk and 11 short papers were carefully reviewed and selected from 88 submiss...
Article
To resolve conflicts among norms,various nonmonotonic formalisms can be used to perform prioritized normative reasoning. Meanwhile, formal argumentation provides a way to represent nonmonotonic logics. In this paper, we propose a representation of prioritized normative reasoning by argumentation. Using hierarchical abstract normative systems, we de...
Conference Paper
The ideal worlds of a possible worlds semantics may satisfy both a primary obligation and an associated secondary obligation, for example the obligation to keep a promise and the obligation to apologise for not keeping it. This is known as the pragmatic oddity introduced by Prakken and Sergot. We argue that an adequate treatment of the pragmatic od...
Conference Paper
The interpretation of a norm is often uncertain and conflicting. In this paper we propose a model for arguing about legal interpretation, which considers the problems of vagueness. After motivating our adoption of graded categories as a tool to tackle the problem of open texture in legal interpretation, we introduce a model based on fuzzy logic and...
Conference Paper
We are interested in formal foundations for enterprise decision support. In this perspective, enterprise architecture is characterised by highly uncertain plans in a changing environment, and translates strategic goals into an IT strategy. Typically there are a large number of stakeholders with conflicting views, communicating plans of action, and...
Article
In this paper we show how the defense relation among abstract arguments can be used to encode the reasons for accepting arguments. After introducing a novel notion of defenses and defense graphs, we propose a defense semantics together with a new notion of defense equivalence of argument graphs, and compare defense equivalence with standard equival...
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This chapter lays down the fundamental ideas and choices on which our approach is based. First, it identifies the needs of architects in the design, communication, realisation, and change of enterprise architectures. It then describes the central role of architecture models in our approach, the use of models in communication, the relationship betwe...
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Enterprise architecture, by nature, requires the interconnection and accumulation of large amounts of information from various sources. An enterprise modelling language, such as the one introduced in Chap. 5, can only be successful if supported by adequate tooling. Visualisation and analysis of architectures, as described in Chaps. 8 and 9, respect...
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This chapter also explains what the added value of enterprise architecture analysis techniques is in addition to existing, more detailed, and domain-specific ones for business processes or software, for example. Analogous to the idea of using the ArchiMate enterprise modelling language to integrate detailed design models, the chapter demonstrates t...
Article
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In an organisational setting such as an online marketplace, an entity called the ‘organisation’ or ‘institution’ defines interaction protocols, monitors agent interaction, and intervenes to enforce the interaction protocols. The organisation might be a software system that thus regulates the marketplace, for example. In this article we abstract ove...
Article
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This article aims to achieve two goals: to show that probability is not the only way of dealing with uncertainty (and even more, that there are kinds of uncertainty which are for principled reasons not addressable with probabilistic means); and to provide evidence that logic-based methods can well support reasoning with uncertainty. For the latter...
Article
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The literature on judgment aggregation is moving from studying impossibility results regarding aggregation rules towards studying specific judgment aggregation rules. Here we give a structured list of most rules that have been proposed and studied recently in the literature, together with various properties of such rules. We first focus on the majo...
Article
L'éditorial est en libre accès et disponible sur le site Web de College Publications : http://www.collegepublications.co.uk/
Article
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In this paper we study AGM contraction and revision of rules using input/output logical theories. We replace propositional formulas in the AGM framework of theory change by pairs of propositional formulas, representing the rule based character of theories, and we replace the classical consequence operator Cn by an input/output logic. The results in...
Chapter
Accessing relevant legal information found in text excerpts from heterogeneous sources is essential to the decision making process in consumer disputes. The Ontology of Relevant Legal Information in Consumer Disputes (ric) is the domain-independent ontology modeling this relevant legal information comprising rights, their requisites, exceptions, co...
Article
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This paper describes the Eunomos software, an advanced legal document and knowledge management system, based on legislative XML and ontologies. We describe the challenges of legal research in an increasingly complex, multi-level and multi-lingual world and how the Eunomos software helps users cut through the information overload to get the legal in...
Article
This report documents the program and the outcomes of Dagstuhl Perspectives Workshop 15362 "Present and Future of Formal Argumentation". The goal of this Dagstuhl Perspectives Workshop was to gather the world leading experts in formal argumentation in order to develop a SWOT (Strength, Weaknesses, Opportunities, Threats) analysis of the current s...
Conference Paper
The AGM theory of belief revision is based on propositional belief sets. In this paper we develop a logic for revision of temporal belief bases, containing expressions about temporal propositions (tomorrow it will rain), possibility (it may rain tomorrow), actions (the robot enters the room) and pre- and post-conditions of these actions. We prove t...
Book
This book constitutes the proceedings of the 13th International Workshop on Computational Logic in Multi-Agent Systems, CLIMA XIII, held in Montpellier, France, in August 2012. The 11 regular papers were carefully reviewed and selected from 27 submissions and presented with three invited papers. The purpose of the CLIMA workshops is to provide a fo...
Article
Full-text available
The literature on judgment aggregation has now been moving from studying impossibility results regarding aggregation rules towards studying specific judgment aggregation rules. Here we focus on a family of rules that is the natural counterpart of the family of Condorcet-consistent voting rules: majority-preserving judgment aggregation rules. A judg...
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In general the problem of verifying whether a structured business process is compliant with a given set of regulations is NP-hard. The present paper focuses on identifying a tractable subset of this problem, namely verifying whether a structured business process is compliant with a single global obligation. Global obligations are those whose validi...
Article
This paper looks at the use of recitals in the int erpretation of EU legislation, and mechanisms for connecting them to normative provisions. The purposive approach to the interpretation of EU legi slation taken by the European Court of Justice makes frequent references to recit als as helping to establish the purpose of normative provisions....
Conference Paper
We study a number of properties concerning the behaviour of semantics for Dung style abstract argumentation when the argumentation framework changes. The properties are concerned with how the evaluation of an argumentation framework changes if an attack between two arguments is added or removed. The results provide insight into the behaviour of the...
Conference Paper
Robot knowledge of the world is created from discrete and asynchronous events received from its perception components. Proper representation and maintenance of robot knowledge is crucial to enable the use of robot knowledge for planning, user-interaction, etc. This paper identifies some of the main issues related to the representation, maintenance...
Article
This papers tackles the fundamental questions arising when looking at argumentation frameworks as interacting components, characterized by an Input/Output behavior, rather than as isolated monolithical entities. This modeling stance arises naturally in some application contexts, like multi-agent systems, but, more importantly, has a crucial impact...
Chapter
It is shown that I/O logic can be based on intuitionistic logic instead of classical logic. More specifically, it is established that, when going intuitionistic, a representation theorem is still available for three of the four (unconstrained) original I/O operations. The trick is to see a maximal consistent set as a saturated one. The axiomatic ch...
Conference Paper
With an increase in regulations, it is challenging for organizations to identify relevant regulations and ensure that their business processes comply with legal provisions. Multiple regulations cover the same domain and can interact with, complement or contradict each other. To overcome these challenges, a systematic approach is required. This pape...
Article
In the last years, argumentation theory has been exploited to reason about norms, argue about enforced obligations and permissions, and establish the validity of norms seen as argumentative claims. In this paper, we start from the dynamic legal argumentation framework recently proposed by Prakken and Sartor, and we extend their ASPIC-based system b...
Article
This paper reviews existing approaches to representing legal knowledge for legal requirements engineering. Legal requirement methodologies are rarely developed together with legal practitioners, with the result that often approaches are based on a simplified view of law which prevents their acceptance by legal practitioners. In this paper, we analy...
Article
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We develop a model of abduction in abstract argumentation, where changes to an argumentation framework act as hypotheses to explain the support of an observation. We present dialogical proof theories for the main decision problems (i.e., finding hypothe- ses that explain skeptical/credulous support) and we show that our model can be instantiated on...
Conference Paper
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In this paper we study three semantics to combine constitutive and regulative norms. In the first semantics, called the simple-minded semantics, the output of the constitutive norms are intermediate facts used as input for the regulative norms. The second method is called throughput, and adds the input of the constitutive norms to the intermediate...
Conference Paper
In this paper we provide a Beth-Reichenbach (BR) semantics capable of analyzing the miners puzzle. We augment the BR-semantics with reactive arrows, obtaining a new semantic that we call ReBR-semantics, and sharpen our analysis to the miners puzzle. We further extend the ReBR-semantics with actions to obtain our final ReBRA-semantics, capable of mo...
Conference Paper
A linguistic analysis of deontic paradoxes can be used to further develop deontic logic. In this paper we provide a Beth-Reichenbach semantics to analyze deontic paradoxes, and we illustrate it on the single agent decision problem of the miners scenario. We also introduce extensions with reactive arrows and actions, which can be used to give a ling...
Conference Paper
Makinson and van der Torre [13] introduce a number of input/output (I/O) logics to reason about conditional norms. The key idea is to make obligations relative to a given set of conditional norms. The meaning of the normative concepts is, then, given in terms of a set of procedures yielding outputs for inputs. Using the same methodology, Stolpe[19,...
Conference Paper
Intention reconsideration is a central challenge in BDI (Belief-Desire-Intention) theory. The intention reconsideration models of the early nineties focus on when a commitment may be reconsidered, for example when it has been achieved, when it is no longer achievable, or when the associated goal has been dropped. In this paper, we create an abstrac...
Book
This book constitutes the proceedings of the 15th International Workshop on Computational Logic in Multi-Agent Systems, CLIMA XV, held in Prague, Czech Republic, in August 2014.The 12 regular papers were carefully reviewed and selected from 20 submissions. The purpose of the CLIMA workshops is to provide a forum for discussing techniques, based on...
Article
In existing literature, little attention has been paid to the problems of how the uncertainty reflected by natural language text (e.g. verbal and linguistic uncertainty) can be explicitly formulated in argumentation schemes, and how argumentation schemes enriched with various types of uncertainty can be exploited to support argumentation mining and...