Caroline Devred

Symmetric argumentation frameworks

This paper is centered on the family of Dungs finite argumentation frameworks when the attacks relation is symmetric (and nonempty and irreflexive). We show that while this family does not contain any well-founded framework, every element of it is both coherent and relatively grounded. Then we focus on the acceptability problems for the various semantics introduced by Dung, yet generalized to sets of arguments. We show that only two distinct forms of acceptability are possible when the considered frameworks are symmetric. Those forms of acceptability are quite simple, but tractable; this contrasts with the general case for which all the forms of acceptability are intractable (except for the ones based on grounded or naive extensions).

Prudent semantics for argumentation frameworks

We present new prudent semantics within Dungs theory of argumentation. Under such prudent semantics, two arguments cannot belong to the same extension whenever one of them attacks indirectly the other one. We argue that our semantics lead to a better handling of controversial arguments than Dungs ones. We compare the prudent inference relations induced by our semantics w.r.t. cautiousness; we also compare them with the inference relations induced by Dungs semantics

A constrained argumentation system for practical reasoning

Practical reasoning (PR), which is concerned with the generic question of what to do, is generally seen as a two steps process: (1) deliberation, in which an agent decides what state of affairs it wants to reach -- that is, its desires; and (2) means-ends reasoning, in which the agent looks for plans for achieving these desires. A desire is justified if it holds in the current state of the world, and feasible if there is a plan for achieving it. The agents intentions are thus a consistent subset of desires that are both justified and feasible. This paper proposes the first argumentation system for PR that computes in one step the intentions of an agent, allowing thus to avoid the drawbacks of the existing systems. The proposed system is grounded on a recent work on constrained argumentation systems, and satisfies the rationality postulates identified in argumentation literature, namely the consistency and the completeness of the results.

Argumentation frameworks as constraint satisfaction problems

This paper studies how to encode the problem of computing the extensions of an argumentation framework (under a given semantics) as a constraint satisfaction problem (CSP). Such encoding is of great importance since it makes it possible to use the very efficient solvers (developed by the CSP community) for computing the extensions. We focus on three families of frameworks: Dungs abstract framework, its constrained version and preference-based argumentation frameworks.

Generating possible intentions with constrained argumentation systems

Practical reasoning (PR), which is concerned with the generic question of what to do, is generally seen as a two steps process: (1) deliberation, in which an agent decides what state of affairs it wants to reach - that is, its desires; and (2) means-ends reasoning, in which the agent looks for plans for achieving these desires. The agents intentions are a consistent set of desires that are achievable together. This paper proposes the first argumentation system for PR that computes in one step the possible intentions of an agent, avoiding thus the drawbacks of the existing systems. The proposed system is grounded on a recent work on constrained argumentation systems, and satisfies the rationality postulates identified in argumentation literature, namely the consistency and the completeness of the results.

Dialectical Proofs for Constrained Argumentation

Constrained argumentation frameworks (CAF) generalize Dungs frameworks by allowing additional constraints on arguments to be taken into account in the definition of acceptability of arguments. These constraints are expressed by means of a logical formula which is added to Dungs framework. The resulting system captures several other extensions of Dungs original system. To determine if a set of arguments is credulously inferred from a CAF, the notion of dialectical proof (alternating pros and cons arguments) is extended for Dungs frameworks in order to respect the additional constraint. The new constrained dialectical proofs are computed by using Answer Set Programming.

Inference from controversial arguments

We present new careful semantics within Dung’s theory of argumentation. Under such careful semantics, two arguments cannot belong to the same extension whenever one of them indirectly attacks a third argument while the other one indirectly defends the third. We argue that our semantics lead to a better handling of controversial arguments than Dung’s ones in some settings. We compare the careful inference relations induced by our semantics w.r.t. cautiousness; we also compare them with the inference relations induced by Dung’s semantics.

Handling Ignorance in Argumentation: Semantics of Partial Argumentation Frameworks

In this paper we propose semantics for acceptablity in partial argumentation frameworks (PAF). The PAF is an extension of Dungs argumentation framework and has been introduced in [1] for merging argumentation frameworks. It consists in adding a new interaction between arguments representing the ignorance about the existence of an attack. The proposed semantics are built following Dungs method, so that they generalize Dungs semantics without increasing the temporal complexity.

ARGUMENTATION AND CP-BOOLEAN GAMES

There already exist some links between argumentation and game theory. For instance, dynamic games can be used for simulating interactions between agents in an argumentation process. In this paper, we establish a new link between these domains in a static framework: we show how an argumentation framework can be translated into a CP-Boolean game and how this translation can be used for computing extensions of argumentation semantics. We give formal algorithms to do so.

Translation of an Argumentation Framework into a CP-Boolean Game

There already exist some links between argumentation and game theory. For instance, dynamic games can be used for simulating interactions between agents in an argumentation process. In this paper, we establish a new link between these domains in a static framework: we show how an argumentation framework can be translated into a CP-Boolean game and how this translation can be used for computing extensions of argumentation semantics. We give formal algorithms to do so.