\begin{tabbing}
$\forall$\=$i$:Id, ${\it ds}$:$x$:Id fp$\rightarrow$ Type, ${\it da}$:$k$:Knd fp$\rightarrow$ Type, $A$:ecl(${\it ds}$;${\it da}$), ${\it snd}$:msg{-}spec(${\it ds}$;${\it da}$), ${\it es}$:ES,\+
\\[0ex]$l$:IdLnk.
\-\\[0ex]source($l$) $=$ $i$ $\Rightarrow$ @$i$[[$A$;${\it snd}$]] $\in$ Prop
\end{tabbing}