$\forall$${\it es}$:ES, $X$, $Y$:AbsInterface(Top). ($\forall$$e$:E. ($\uparrow$($e$ $\in_{b}$ $X$)) $\Rightarrow$ ($\uparrow$($e$ $\in_{b}$ $Y$))) $\Rightarrow$ (E($X$) $\subseteq$r E($Y$))