\begin{tabbing}
$\forall$\=$A$, $B$:Type, $f$:($A$$\rightarrow$($B$ + Top)), ${\it ds}$:(Id$\rightarrow$Type), ${\it da}$:(Id$\rightarrow$Knd$\rightarrow$Type), $X$:Interface(${\it ds}$;${\it da}$;$A$),\+
\\[0ex]${\it es}$:ES.
\-\\[0ex]es{-}decl(${\it es}$;${\it ds}$;${\it da}$)
\\[0ex]$\Rightarrow$ ($\forall$$e$:E. ($e$ $\in_{b}$ [[interface{-}compose($f$;$X$)]]) = (($e$ $\in_{b}$ [[$X$]]) $\wedge_{b}$ can{-}apply($f$;[[$X$]]($e$))) $\in$ $\mathbb{B}$)
\end{tabbing}