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Utilizing ASP for generating and visualizing argumentation frameworks
 CoRR
"... Abstract. Within the area of computational models of argumentation, the instantiationbased approach is gaining more and more attention, not at least because meaningful input for Dung’s abstract frameworks is provided in that way. In a nutshell, the aim of instantiationbased argumentation is to fo ..."
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Abstract. Within the area of computational models of argumentation, the instantiationbased approach is gaining more and more attention, not at least because meaningful input for Dung’s abstract frameworks is provided in that way. In a nutshell, the aim of instantiationbased argumentation is to form, from a given knowledge base, a set of arguments and to identify the conflicts between them. The resulting network is then evaluated by means of extensionbased semantics on an abstract level, i.e. on the resulting graph. While several systems are nowadays available for the latter step, the automation of the instantiation process itself has received less attention. In this work, we provide a novel approach to construct and visualize an argumentation framework from a given knowledge base. The system we propose relies on AnswerSet Programming and follows a twostep approach. A first program yields the logicbased arguments as its answersets; a second program is then used to specify the relations between arguments based on the answersets of the first program. As it turns out, this approach not only allows for a flexible and extensible tool for instantiationbased argumentation, but also provides a new method for answerset visualization in general. 1
Maxiconsistent operators in argumentation
 In 20th European Conference on Artificial Intelligence (ECAI’12
, 2012
"... Abstract. This paper studies an instantiation of Dungstyle argumentation system with classical propositional logic. Our goal is to explore the link between the result obtained by using argumentation to deal with an inconsistent knowledge base and the result obtained by using maximal consistent sub ..."
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Abstract. This paper studies an instantiation of Dungstyle argumentation system with classical propositional logic. Our goal is to explore the link between the result obtained by using argumentation to deal with an inconsistent knowledge base and the result obtained by using maximal consistent subsets of the same knowledge base. Namely, for a given attack relation and semantics, we study the question: does every extension of the argumentation system correspond to exactly one maximal consistent subset of the knowledge base? We study the class of attack relations which satisfy that condition. We show that such a relation must be conflictdependent, must not be valid, must not be conflictcomplete, must not be symmetric etc. Then, we show that some attack relations serve as lower or upper bounds with respect to the condition we study (e.g. we show that if an attack relation contains “canonical undercut ” then it does not satisfy this condition). By using our results, we show for each attack relation and each semantics whether or not they satisfy the aforementioned condition. Finally, we interpret our results and discuss more general questions, like does (and when) this link is a desirable property. This work will help us obtain our longterm goal, which is to better understand the role of argumentation and, more particularly, the expressivity of logicbased instantiations of Dungstyle argumentation frameworks. 1
On extended conflictfreeness in argumentation
 In Proceedings of the 24th Benelux Conference on Artificial Intelligence (BNAIC’12
, 2012
"... This paper studies a possibility to represent nary conflicts within an argumentation framework having only binary attacks. We show that different instantiations of the abstract argumentation framework defined by Dung use very similar constructs for dealing with nary conflicts. We start by studying ..."
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This paper studies a possibility to represent nary conflicts within an argumentation framework having only binary attacks. We show that different instantiations of the abstract argumentation framework defined by Dung use very similar constructs for dealing with nary conflicts. We start by studying this procedure on two fullyinstantiated systems from the argumentation literature and then show that it can also be formalised on the abstract level. We argue that this way of handling nary conflicts has two benefits. First, it allows to represent all the information within a standard argumentation framework, only by using arguments and attacks (e.g. without adding a new component to store the sets of conflicts). Second, all the level is conceptually clear. 1
Identifying the Class of MaxiConsistent Operators in Argumentation
"... Dung’s abstract argumentation theory can be seen as a general framework for nonmonotonic reasoning. An important question is then: what is the class of logics that can be subsumed as instantiations of this theory? The goal of this paper is to identify and study the large class of logicbased instan ..."
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Dung’s abstract argumentation theory can be seen as a general framework for nonmonotonic reasoning. An important question is then: what is the class of logics that can be subsumed as instantiations of this theory? The goal of this paper is to identify and study the large class of logicbased instantiations of Dung’s theory which correspond to the maxiconsistent operator, i.e. to the function which returns maximal consistent subsets of an inconsistent knowledge base. In other words, we study the class of instantiations where every extension of the argumentation system corresponds to exactly one maximal consistent subset of the knowledge base. We show that an attack relation belonging to this class must be conflictdependent, must not be valid, must not be conflictcomplete, must not be symmetric etc. Then, we show that some attack relations serve as lower or upper bounds of the class (e.g. if an attack relation contains canonical undercut then it is not a member of this class). By using our results, we show for all existing attack relations whether or not they belong to this class. We also define new attack relations which are members of this class. Finally, we interpret our results and discuss more general questions, like: what is the added value of argumentation in such a setting? We believe that this work is a first step towards achieving our longterm goal, which is to better understand the role of argumentation and, particularly, the expressivity of logicbased instantiations of Dungstyle argumentation frameworks. 1.
RESEARCH ARTICLE Logical limits of abstract argumentation frameworks
, 2012
"... Dung’s argumentation framework takes as input two abstract entities: a set of arguments and a binary relation encoding attacks between these arguments. It returns acceptable sets of arguments, called extensions, wrt a given semantics. While the abstract nature of this setting is seen as a great adva ..."
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Dung’s argumentation framework takes as input two abstract entities: a set of arguments and a binary relation encoding attacks between these arguments. It returns acceptable sets of arguments, called extensions, wrt a given semantics. While the abstract nature of this setting is seen as a great advantage, it induces a big gap with the application that it is used to. This raises some questions about the compatibility of the setting with a logical formalism (i.e., whether it is possible to instantiate it properly from a logical knowledge base), and about the significance of the various semantics in the application context. In this paper we tackle the above questions. We first propose to fill in the previous gap by extending Dung’s framework. The idea is to consider all the ingredients involved in an argumentation process. We start with the notion of an abstract monotonic logic which consists of a language (defining the formulas) and a consequence operator. We show how to build, in a systematic way, arguments from a knowledge base formalized in such a logic. We then recall some basic postulates that any instantiation should satisfy. We study how to choose an attack relation so that the instanti