Justifying answer sets using argumentation

Claudia Schulz
Francesca Toni
Department of Computing, Imperial College London


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.

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journal = {Theory and Practice of Logic Programming},
publisher = {Cambridge University Press},
author = {Claudia Schulz and Francesca Toni},
title = {Justifying answer sets using argumentation},
volume = {16},
number = {1},
year = {2016},
pages = {59–110}