\begin{tabbing}
$\forall$\=$S$, $V$:Type, $M$:(IdLnk$\rightarrow$Id$\rightarrow$Type), $l$:IdLnk, $s$:$S$, $v$:$V$,\+
\\[0ex]$L$:(($t$:Id $\times$ ($S$$\rightarrow$$V$$\rightarrow$($M$($l$,$t$) List))) List).
\-\\[0ex]tagged{-}messages($l$;$s$;$v$;$L$) $\in$ (\{$m$:Msg($M$)$\mid$ mlnk($m$) = $l$\}  List)
\end{tabbing}