Coalition Graph

The coalition graph of a BAF $B = (A, R, S)$ is the AF $F^{\mathsf{Coal}}_B = (\mathsf{Coal}(B), R^{\mathsf{Coal}}_B)$, where $\mathsf{Coal}(B)$ is the set of coalitions of $B$ and $(C_1, C_2) \in R^{\mathsf{Coal}}_B$ iff $(a, b) \in R$ for some $a \in C_1$, $b \in C_2$.