Contribution Functions for Quantitative Bipolar Argumentation Graphs: A Principle-based Analysis

In formal argumentation, arguments and their relations are typically represented as directed graphs, in which nodes are arguments and edges are argument relationships (typically: attack or support). From these argumentation graphs, inferences about the acceptability statuses or strengths of arguments are drawn. One formal argumentation approach that is gaining increased research attention is Quantitative Bipolar Argumentation (QBA). In QBA, (typically numerical) weights - so-called initial strengths - are assigned to arguments, and arguments are connected by a support and an attack relation. Hence, arguments directly connected to a node through the node's incoming edges can be referred to as attackers and supporters (depending on the relation). Given a Quantitative Bipolar Argumentation Graph (QBAG), an argumentation semantics then infers the arguments' final strengths; intuitively, an argument's attackers tend to decrease its final strength, whereas supporters tend to increase it.