$\forall$$l_{1}$,$l_{2}$:IdLnk, ${\it tg}_{1}$,${\it tg}_{2}$:Id.
\\[0ex](rcv($l_{1}$,${\it tg}_{1}$) = rcv($l_{2}$,${\it tg}_{2}$) $\in$ Knd) $\Rightarrow$ guard((($l_{1}$ = $l_{2}$) $\wedge$ (${\it tg}_{1}$ = ${\it tg}_{2}$)))