Analysis and Implementation of scf2 Argumentation Semantics

Master's thesis by Guzel Khuziakhmetova

Supervisor Sebastian Rudolph, Sarah Alice Gaggl
Logische Programmierung und Argumentation
1 Juli 2020 – 25 Februar 2021

Abstract argumentation is an approach to effect a formal treatment of non-monotonic human reasoning. There are arguments, that are "atomic", and attack relations between arguments. Together they make an argumentation framework. In abstract argumentation, there exist paradoxes that are typical to encounter in argumentation frameworks of a certain type. Particularly, paradoxical behavior was detected in the argumentation frameworks containing self-attacking arguments and odd-length attack cycles. The newly invented scf2 argumentation semantics, which is in the center of the current thesis, is aiming to solve both problems.

Scf2 was initially introduced and studied in the paper of Cramer and Guillaume [12]. It is based on cf2 semantics and is considered to be the first semantics that can solve the odd- length cycle problem. Remarkable that this semantics also manages to preserve properties that must be satisfied by any semantics which claims to be a reliable one. The original paper introduces two new principles, defines scf2, and proves that it satisfies both new principles. Additionally, it discusses the findings of a recent empirical cognitive study. It does not provide a full analysis of the semantics and serves more as a good starting point for further research. This thesis contributes to the analysis of scf2 as well as provides its implementation. In this paper, we continued semantics’ evaluation according to the properties that are relevant for naive-based semantics, determined its computational complexity, and compared it against other semantics. We developed a direct implementation for computing scf2 extensions and checked the performance of the code on input data of different structures.