Strength Change Explanations in Quantitative Argumentation

TL;DR

This paper introduces a method for explaining how changes in argument strengths within quantitative argumentation graphs can lead to desired inference outcomes, enhancing the contestability of argumentation-based reasoning.

Contribution

It formalizes strength change explanations, connects them to inverse and counterfactual problems, and demonstrates their properties and applicability through heuristic search.

Findings

Strength change explanations can be systematically derived for layered graphs.

Existence of explanations is proven in certain cases, with limitations identified.

Heuristic search effectively finds explanations in typical scenarios.

Abstract

In order to make argumentation-based inference contestable, it is crucial to explain what changes can achieve a desired (instead of the contested) inference result. To this end, we introduce strength change explanations for quantitative (bipolar) argumentation graphs. Strength change explanations describe changes to the initial strengths of a subset of the arguments in a given graph that can achieve a desired ordering based on the final strengths of some (potentially different) subset of arguments. We show that the existing notions of inverse and counterfactual problems can be reduced to strength change explanations. We also prove basic soundness and completeness properties of our strength change explanations, and demonstrate their existence and non-existence in some special cases. By applying a heuristic search, we demonstrate that we can often successfully find strength change explanations for layered graphs that are common in typical application scenarios; still, limitations remain for settings where we do not provide guarantees for the presence (or absence) of explanations.