Dynamics in argumentation with single extensions: attack refinement and the grounded extension

We introduce nine attack refinement principles stating whether the extension stays the same if we add a single attack, and we show that the grounded extension satisfies five of them. We define also an extension called acyclic attack refinement by adding a loop condition, and we show that the grounded extension satisfies one of the acyclic attack refinement principles. Moreover, we define an extension called conditional attack refinement taking alternative attackers into account, and we give an example of a conditional attack refinement principle satisfied by the grounded extension.