$\forall$$T$:Type, $L$:($T$ List), $R$:(\{$x$:$T$$\mid$ ($x$ $\in$ $L$)\} $\rightarrow$Realizer), $x$:$T$, $B$:Realizer.
\\[0ex]($x$ $\in$ $L$) $\Rightarrow$ $\oplus$$x$$\in$$L$.$R$($x$) $\subseteq$ $B$ $\Rightarrow$ $R$($x$) $\subseteq$ $B$