$\forall$$l$:IdLnk, ${\it dt}$:${\it tg}$:Id fp$\rightarrow$ Type, ${\it tg}$:Id, $T$:Type. lnk{-}decl($l$;${\it dt}$)(rcv($l$,${\it tg}$))?$T$ $\sim$ ${\it dt}$(${\it tg}$)?$T$