Attacks)$ and an argumentation semantics $\sigma_x$, an argument $a \in AR$ is skeptically accepted iff it is contained in *all* of the extensions of $\sigma_x(AF)$. The skeptical extension of an argumentation framework $AF$ is the intersection of all extensions $\sigma_x(AF)$ (*a.i.*, $\sigma^{\cap}_x(AF) := \bigcap_{E \in \sigma_x(AF)} E $).

-   **Lenient Acceptance.** Given an argumentation framework\
    $AF = (AR, Attacks)$ and an argumentation semantics $\sigma_x$, the *lenient* extension of $AF$ is the union of all extensions $\sigma_x(AF)$ (*a.i.*, $\sigma^{\cup}_x(AF) := \bigcup_{E \in \sigma_x(AF)} E$).

Let us note that the extensions returned by lenient semantics are not necessarily conflict-free.

Given the variety of argumentation semantics that have been established throughout the years, it can be challenging to assess which semantics are suitable for a specific application. Consequently, *argumentation principles* have been established; evaluating the compliance with one or multiple principles can guide the assessment of argumentation semantics in the context of a specific use case. For example, a principle can specify that an argumentation semantics should prescribe exactly one extension for any argumentation framework. An overview of argumentation principles is provided by van der Torre and Vesic [@van2017principle].

Argumentation Expansions
------------------------

To describe a specific type of relation between two argumentation frameworks, 