Strong Admissibility Revisited

Preprin

A QBF-based Formalization of Abstract Argumentation Semantics

Supported by the National Research Fund, Luxembourg (LAAMI project) and by the Engineering and Physical Sciences Research Council (EPSRC, UK), grant ref. EP/J012084/1 (SAsSY project).Peer reviewedPostprin

Welfare reform in the United States. A descriptive policy analysis

Poverty alleviation is an important objective of European countries and of the United States. If these ‘rich’ states offer elaborate systems of income maintenance, why is there still a considerable amount of poverty? And why are anti-poverty outcomes so different in the United States compared to European countries? This paper completes a trilogy of cross-country research papers on anti-poverty policy. Two former papers analyzed the effects of social transfers on both poverty levels and poverty alleviation through tax and social transfer systems. These papers marked the United States as an outlier: high poverty rates, low public social spending but high private social expenditures, a rather strong belief that people are poor because of laziness or lack of will, and remarkable differences across the Federal States caused by state discretion. Therefore, this paper analyzes U.S. welfare in more detail; we focus on part of the major welfare reform in 1996. The 1996 welfare reform emphasizes an American preference for work. Indeed, the welfare reform increased work, although the earnings of most individuals who left welfare were still below the poverty line, even many years after their exit. A drawback of this work-first approach is the termination of cash assistance after 5 years, especially for vulnerable groups with low skills. Recent economic recession can cause severe troubles; one could - for example – argue that recipients who reach time limits without meeting work requirements should be offered a chance to work in community service jobs in return for cash assistance. We found huge variation of welfare eligibility rights across states, depending on ability to pay and preferences to meet a certain level of social standard and other (social) objectives such as child care, work support and employment programs.welfare reform, poverty

Rationality postulates: applying argumentation theory for non-monotonic reasoning

The current book chapter examines how to apply Dung’s theory of abstract argumentation to define meaningful forms of nonmonotonic inference. The idea is that arguments are constructed using strict and defeasible inference rules, and that it is then examined how these arguments attack (or defeat) each other. The thus defined argumentation framework provides the basis for applying Dung-style semantics, yielding a number of extensions of arguments. As each of the constructed arguments has a conclusion, an extension of arguments has an associated extension of conclusions. It are these extensions of conclusions that we are interested in. In particular, we ask ourselves whether each of these extensions is (1) consistent, (2) closed under the strict inference rules and (3) free from undesired interference. We examine the current generation of techniques to satisfy these properties, and identify some research issues that are yet to be dealt with

Argumentation semantics as formal discussion

In the current chapter, we interpret a number of mainstream argumentation semantics by means of structured discussion. The idea is that an argument is justified according to a particular argumentation semantics iff it is possible to win a discussion of a particular type. Hence, different argumentation semantics correspond to different types of discussion. Our aim is to provide an overview of what these discussions look like, and their formal correspondence to argumentation semantics

Manipulation in group argument evaluation.

Given an argumentation framework and a group of agents, the individuals may have divergent opinions on the status of the arguments. If the group needs to reach a common po- sition on the argumentation framework, the question is how the individual evaluations can be mapped into a collective one. This problem has been recently investigated in [1]. In this paper, we study under which conditions these operators are Pareto optimal and whether they are manipulable.Collective decision making; Argumentation; Judgment aggregation; Social choice theory;

Manipulation in Group Argument Evaluation.

Given an argumentation framework and a group of agents, the individuals may have divergent opinions on the status of the arguments. If the group needsto reach a common position on the argumentation framework, the question is how the individual evaluations can be mapped into a collective one. Thisproblem has been recently investigated by Caminada and Pigozzi. In this paper, we investigate the behaviour of two of such operators from a socialchoice-theoretic point of view. In particular, we study under which conditions these operators are Pareto optimal and whether they are manipulable.Social choice theory; Judgment aggregation; Argumentation; Collective decision making;

On the equivalence between logic programming semantics and argumentation semantics

This work has been supported by the National Research Fund, Luxembourg (LAAMI project), by the Engineering and Physical Sciences Research Council (EPSRC, UK), grant Ref. EP/J012084/1 (SAsSy project), by CNPq (Universal 2012 – Proc. 473110/2012-1), and by CNPq/CAPES (Casadinho/PROCAD 2011).Peer reviewedPreprin

Pareto Optimality and Strategy Proofness in Group Argument Evaluation (Extended Version)

An inconsistent knowledge base can be abstracted as a set of arguments and a defeat relation among them. There can be more than one consistent way to evaluate such an argumentation graph. Collective argument evaluation is the problem of aggregating the opinions of multiple agents on how a given set of arguments should be evaluated. It is crucial not only to ensure that the outcome is logically consistent, but also satisfies measures of social optimality and immunity to strategic manipulation. This is because agents have their individual preferences about what the outcome ought to be. In the current paper, we analyze three previously introduced argument-based aggregation operators with respect to Pareto optimality and strategy proofness under different general classes of agent preferences. We highlight fundamental trade-offs between strategic manipulability and social optimality on one hand, and classical logical criteria on the other. Our results motivate further investigation into the relationship between social choice and argumentation theory. The results are also relevant for choosing an appropriate aggregation operator given the criteria that are considered more important, as well as the nature of agents' preferences

A dialectical approach for argument-based judgment aggregation

The current paper provides a dialectical interpretation of the argumentation-based judgment aggregation operators of Caminada and Pigozzi. In particular, we define discussion-based proof procedures for the foundational concepts of down-admissible and up-complete. We then show how these proof procedures can be used as the basis of dialectical proof procedures for the sceptical, credulous and super credulous judgment aggregation operators