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Instantiating abstract argumentation with classical logic arguments: Postulates and properties. (2011)

by N Gorogiannis, A Hunter
Venue:Artificial Intelligence
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A general account of argumentation with preferences

by Sanjay Modgil, Henry Prakken - ARTIFICIAL INTELLIGENCE , 2012
"... This paper builds on the recent ASPIC+ formalism, to develop a general framework for argumentation with preferences. We motivate a revised definition of con-flict free sets of arguments, adapt ASPIC+ to accommodate a broader range of instantiating logics, and show that under some assumptions, the re ..."
Abstract - Cited by 32 (7 self) - Add to MetaCart
This paper builds on the recent ASPIC+ formalism, to develop a general framework for argumentation with preferences. We motivate a revised definition of con-flict free sets of arguments, adapt ASPIC+ to accommodate a broader range of instantiating logics, and show that under some assumptions, the resulting framework satisfies key properties and rationality postulates. We then show that the generalised framework accommodates Tarskian logic instantiations extended with preferences, and then study instantiations of the framework by classical logic ap-proaches to argumentation. We conclude by arguing that ASPIC+’s modelling of defeasible inference rules further testifies to the generality of the framework, and then examine and counter recent critiques of Dung’s framework and its extensions to accommodate preferences.
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... first to show satisfaction of [18]’s rationality postulates for Tarskian logic instantiations with and without preferences. Following this, we reconstruct classical logic approaches to argumentation =-=[12, 13, 26]-=-, including those that additionally accommodate preferences [5]. To the best of our knowledge, we are the first to prove [18]’s postulates for classical logic approaches with preferences. Finally, we ...

Graduality in argumentation

by Claudette Cayrol - Journal of Artificial Intelligence Research , 1998
"... Argumentation is based on the exchange and valuation of interacting arguments, followed by the selection of the most acceptable of them (for example, in order to take a decision, to make a choice). Starting from the framework proposed by Dung in 1995, our purpose is to introduce “graduality ” in the ..."
Abstract - Cited by 30 (0 self) - Add to MetaCart
Argumentation is based on the exchange and valuation of interacting arguments, followed by the selection of the most acceptable of them (for example, in order to take a decision, to make a choice). Starting from the framework proposed by Dung in 1995, our purpose is to introduce “graduality ” in the selection of the best arguments, i.e. to be able to partition the set of the arguments in more than the two usual subsets of “selected ” and “non-selected ” arguments in order to represent different levels of selection. Our basic idea is that an argument is all the more acceptable if it can be preferred to its attackers. First, we discuss general principles underlying a “gradual ” valuation of arguments based on their argumentation system. Then, we introduce “graduality ” in the concept of acceptability of arguments. We propose new acceptability classes and a refinement of existing classes taking advantage of an available “gradual ” valuation. 1.
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...few intuitive postulates. 1 Introduction There are two major categories of instantiations of Dung’s abstract argumentation framework [4]. A category uses deductive logics (such as propositional logic =-=[2, 6]-=- or Tarskian logics [1]). The second category uses rule-based languages [3, 5, 7] which distinguish between facts, strict rules (they encode strict information), and defeasible rules (they describe ge...

On the Equivalence of Logic-Based Argumentation Systems

by Leila Amgoud, Srdjan Vesic - Proceedings of the 5th International Conference on Scalable Uncertainty Management (SUM 2011), volume 6929 of Lecture Notes in Computer Science , 2011
"... Abstract. Equivalence between two argumentation systems means mainly that the two systems return the same outputs. It can be used for different purposes, namely in order to show whether two systems that are built over the same knowl-edge base but with distinct attack relations return the same output ..."
Abstract - Cited by 14 (9 self) - Add to MetaCart
Abstract. Equivalence between two argumentation systems means mainly that the two systems return the same outputs. It can be used for different purposes, namely in order to show whether two systems that are built over the same knowl-edge base but with distinct attack relations return the same outputs, and more importantly to check whether an infinite system can be reduced into a finite one. Recently, the equivalence between abstract argumentation systems was investi-gated. Two categories of equivalence criteria were particularly proposed. The first category compares directly the outputs of the two systems (e.g. their extensions) while the second compares the outputs of their extended versions (i.e. the sys-tems augmented by the same set of arguments). It was shown that only identical systems are equivalent w.r.t. those criteria. In this paper, we study when two logic-based argumentation systems are equiva-lent. We refine existing criteria by considering the internal structure of arguments and propose new ones. Then, we identify cases where two systems are equivalent. In particular, we show that under some reasonable conditions on the logic under-lying an argumentation system, the latter has an equivalent finite subsystem. This subsystem constitutes a threshold under which arguments of the system have not yet attained their final status and consequently adding a new argument may result in status change. From that threshold, the statuses of all arguments become stable. 1
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.... A study on how to choose an appropriate attack relation was recently carried out by Amgoud and Besnard [1]. Some basic properties of an attack relation were also discussed by Gorogiannis and Hunter =-=[8]-=-. Examples of such properties are recalled below. C1 ∀a, b, c ∈ A, if Conc(a) ≡ Conc(b) then aRc iff bRc C2 ∀a, b, c ∈ A, if Supp(a) = Supp(b) then cRa iff cRb The first property says that two argumen...

Normal and strong expansion equivalence for argumentation frameworks

by Ringo Baumann - Artificial Intelligence
"... Given a semantics σ, two argumentation frameworks (AFs) F and G are said to be standard equivalent if they possess the same extensions and strongly equiva-lent if, for any AF H, F conjoined with H and G conjoined with H are standard equivalent. Argumentation is a dynamic process and, in general, new ..."
Abstract - Cited by 8 (5 self) - Add to MetaCart
Given a semantics σ, two argumentation frameworks (AFs) F and G are said to be standard equivalent if they possess the same extensions and strongly equiva-lent if, for any AF H, F conjoined with H and G conjoined with H are standard equivalent. Argumentation is a dynamic process and, in general, new arguments occur in response to a former argument or, more precisely, attack a former ar-gument. For this reason, rather than considering arbitrary expansions we focus here on expansions where new arguments and attacks may be added but the attacks among the old arguments remain unchanged. We define and character-ize two new notions of equivalence between AFs (which lie in-between standard and strong equivalence), namely normal and strong expansion equivalence. Fur-thermore, using the characterization theorems proved in this paper, we draw the connections between all mentioned notions of equivalence including further equivalence relations, so-called weak and local expansion equivalence.
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... of new attacks between existing arguments may occur if the underlying attack definition is changed and the abstract AF has to re-instantiated. A detailed analysis of attack-relations can be found in =-=[27]-=-. 3.4. Preliminary Relations Now we present some preliminary relations between the mentioned notions of equivalence. The presented implications follow directly from Definitions 3, 4 and 6. Figure 1 su...

Generalizations of Dung frameworks and their role in formal argumentation

by Gerhard Brewka, Sylwia Polberg, Stefan Woltran - Intelligent Systems, IEEE, PP(99), 2013. In
"... Abstract. The aim of this paper is to provide a short survey of some of the most popular abstract argumentation frameworks available today. We present the gen-eral idea of abstract argumentation, highlighting the role of abstract frameworks in the argumentation process and review the original Dung f ..."
Abstract - Cited by 6 (2 self) - Add to MetaCart
Abstract. The aim of this paper is to provide a short survey of some of the most popular abstract argumentation frameworks available today. We present the gen-eral idea of abstract argumentation, highlighting the role of abstract frameworks in the argumentation process and review the original Dung frameworks and their semantics. Then a discussion on generalizations of these frameworks is given, focusing on structures taking preferences and values into account and approaches where not only attack but also support relations can be modeled. Finally we re-view the concept of abstract dialectical frameworks, one of the most general sys-tems for abstract argumentation providing a flexible, principled representation of arbitrary argument relations.
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...: logic–based and abstract approaches. The former (see for instance [16]) takes the logical structure of arguments into account and defines notions like attack, undercut, defensibility etc. (see e.g. =-=[43]-=-) in terms of logical properties of the chosen argument structures. In contrast, abstract approaches - which will be the topic of this paper - consider arguments as atomic items, focusing entirely on ...

Rich preference-based argumentation frameworks

by Leila Amgoud, Srdjan Vesic , 2014
"... An argumentation framework is seen as a directed graph whose nodes are arguments and arcs are attacks between those arguments. Acceptable sets of arguments, called extensions, are computed using an acceptability semantics. In this paper, we study how preferences issued from differences in strengths ..."
Abstract - Cited by 5 (2 self) - Add to MetaCart
An argumentation framework is seen as a directed graph whose nodes are arguments and arcs are attacks between those arguments. Acceptable sets of arguments, called extensions, are computed using an acceptability semantics. In this paper, we study how preferences issued from differences in strengths of arguments can help in argumentation frameworks. We first explain that they play two key roles: i) to repair the attack relation be-tween arguments, ii) to refine the evaluation of arguments. We show that the two roles are independent and need different procedures for modelling them. In a second part of this paper, after showing that existing systems that treat the first role of preferences do not perform well in certain situ-ations, we propose and study a new abstract and general system which is capable of treating properly both roles of preferences. The third part of this work is devoted to defining a bridge between the argumentation-based and the coherence-based approaches for handling inconsistency in knowl-edge bases, in particular when priorities between formulas are available. We focus on two well-known models, namely the preferred sub-theories intro-duced by Brewka and the demo-preferred sets defined by Cayrol, Royer and framework which is in full correspondence with it.
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... applied for reasoning about inconsistent information, this relation captures the logical inconsistency of a knowledge base. An example of relation is the so-called undercut and proposed in [30] (see =-=[31]-=- for more attack relations in case of systems built over propositional knowledge bases). Definition 3 (Undercut). An argument (H,h) undercuts an argument (H ′, h′) iff ∃h′′ ∈ H ′ such that h ≡ ¬h′′. T...

On the equivalence between logic programming semantics and argumentation semantics

by Martin Caminada , Samy Sá , João Alcântara , Wolfgang Dvořák , 2013
"... Abstract In the current paper, we re-examine the connection between formal argumentation and logic programming from the perspective of semantics. We observe that one particular translation from logic programs to instantiated argumentation (the one described by Wu, Caminada and Gabbay) is able to se ..."
Abstract - Cited by 4 (1 self) - Add to MetaCart
Abstract In the current paper, we re-examine the connection between formal argumentation and logic programming from the perspective of semantics. We observe that one particular translation from logic programs to instantiated argumentation (the one described by Wu, Caminada and Gabbay) is able to serve as a basis for describing various equivalences between logic programming semantics and argumentation semantics. In particular, we are able to show equivalence between regular semantics for logic programming and preferred semantics for formal argumentation. We also show that there exist logic programming semantics (L-stable semantics) that cannot be captured by any abstract argumentation semantics.
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...ever, are relevant for more than just the connection between logic programming and formal argumentation. They also shed light on specific aspects of instantiated argumentation theory in general (e.g. =-=[3, 11, 10]-=-). In particular we show 1 the connection between argument-labellings at the abstract level and conclusion-labellings at the instantiated level. With one notable exception, we are able to show that ma...

Context-free and Context-sensitive kernels: Update and deletion equivalence in abstract argumentation

by Ringo Baumann - In ECAI , 2014
"... Abstract. Notions of equivalence which guarantee inter-substitutability w.r.t. further modifications have received considerable interest in nonmonotonic reasoning. This paper is within the context of abstract argumentation and we focus on the most general form of a dynamic scenarios, so-called updat ..."
Abstract - Cited by 4 (4 self) - Add to MetaCart
Abstract. Notions of equivalence which guarantee inter-substitutability w.r.t. further modifications have received considerable interest in nonmonotonic reasoning. This paper is within the context of abstract argumentation and we focus on the most general form of a dynamic scenarios, so-called updates as well as certain sub-classes, namely local, normal and arbitrary deletions. We provide characteri-zation theorems for the corresponding equivalence notions and draw the relations to the recently proposed kinds of expansion equivalence [15, 3]. Many of the results rely on abstract concepts like context-free kernels or semantics satisfying isolate-inclusion. Therefore, the re-sults may apply to future semantics as well as further equivalence notions. 1
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...ions naturally appear. For instance, normal and local expansions correspond to re-instantiations if a new piece of information is added [3] or if we change to a less restrictive notion of attack (see =-=[13]-=- for different attack relations). In this paper we study the most general form of a dynamic scenario, so-called update where adding as well as deleting of arguments and attacks is allowed. Furthermore...

Utilizing ASP for generating and visualizing argumentation frameworks

by Johannes Peter Wallner, Stefan Woltran - CoRR
"... Abstract. Within the area of computational models of argumentation, the instan-tiation-based 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 instantiation-based argumentation is to fo ..."
Abstract - Cited by 4 (0 self) - Add to MetaCart
Abstract. Within the area of computational models of argumentation, the instan-tiation-based 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 instantiation-based 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 extension-based semantics on an abstract level, i.e. on the resulting graph. While several systems are nowa-days 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 Answer-Set Programming and follows a two-step approach. A first program yields the logic-based arguments as its answer-sets; a second program is then used to specify the relations between arguments based on the answer-sets of the first program. As it turns out, this approach not only allows for a flexible and extensible tool for instantiation-based argumentation, but also provides a new method for answer-set visualization in general. 1
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...emantically equivalent. This restriction comes with a disadvantage however, as the set of pre-defined claims must be chosen with care, since inconsistent conclusions might be drawn otherwise. Indeed, =-=[17]-=- identify conditions for rational and consistent end results, which require the existence of specific arguments, which must be included in C. On the other hand, this restriction is in line with the co...

Maxi-consistent operators in argumentation

by Srdjan Vesic - In 20th European Conference on Artificial Intelligence (ECAI’12 , 2012
"... Abstract. This paper studies an instantiation of Dung-style argu-mentation 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 ..."
Abstract - Cited by 3 (3 self) - Add to MetaCart
Abstract. This paper studies an instantiation of Dung-style argu-mentation 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 ques-tion: 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 conflict-dependent, must not be valid, must not be conflict-complete, 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 aforemen-tioned condition. Finally, we interpret our results and discuss more general questions, like does (and when) this link is a desirable prop-erty. This work will help us obtain our long-term goal, which is to better understand the role of argumentation and, more particularly, the expressivity of logic-based instantiations of Dung-style argumen-tation frameworks. 1
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...ion is based on the abstract argumentation theory proposed by Dung [11]. This paper studies the case when Dung’s framework is instantiated by building arguments in classical propositional logic (e.g. =-=[4, 12]-=-). The advantages of such an approach are that it can benefit from all the results proved in the case of abstract argumentation, and in addition, it allows for using some important and useful notions ...

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