  Argumentation is a formalism allowing to reason with contradictory
information by modeling arguments and their interactions. There are now an
increasing number of gradual semantics and impact measures that have emerged to
facilitate the interpretation of their outcomes. An impact measure assesses,
for each argument, the impact of other arguments on its score. In this paper,
we refine an existing impact measure from Delobelle and Villata and introduce a
new impact measure rooted in Shapley values. We introduce several principles to
evaluate those two impact measures w.r.t. some well-known gradual semantics.
This comprehensive analysis provides deeper insights into their functionality
and desirability.
