$\forall$${\it poss}$:(ES\{i\}$\rightarrow\mathbb{P}$\{i'\}), $e_{1}$, $e_{2}$:possible{-}event\{i:l\}(${\it poss}$). poss{-}le\{i:l\}($e_{1}$; $e_{2}$) $\in$ $\mathbb{P}$\{i'\}