Justifying Answer Sets using Argumentation

TL;DR

This paper introduces argumentation-based methods to justify why certain literals are included or excluded in answer sets, enhancing interpretability of logic programming results.

Contribution

It presents two novel justification techniques using argumentation theory, linking answer sets to stable extensions and admissible fragments within the ABA framework.

Findings

Attack Trees provide argumentation-based explanations.

ABA-Based Justifications relate to admissible fragments.

Methods improve understanding of answer set composition.

Abstract

An answer set is a plain set of literals which has no further structure that would explain why certain literals are part of it and why others are not. We show how argumentation theory can help to explain why a literal is or is not contained in a given answer set by defining two justification methods, both of which make use of the correspondence between answer sets of a logic program and stable extensions of the Assumption-Based Argumentation (ABA) framework constructed from the same logic program. Attack Trees justify a literal in argumentation-theoretic terms, i.e. using arguments and attacks between them, whereas ABA-Based Answer Set Justifications express the same justification structure in logic programming terms, that is using literals and their relationships. Interestingly, an ABA-Based Answer Set Justification corresponds to an admissible fragment of the answer set in question, and an Attack Tree corresponds to an admissible fragment of the stable extension corresponding to this answer set.