$\forall$$M_{1}$, $M_{2}$:MsgA. $M_{1}$ $\subseteq$ $M_{2}$ $\Rightarrow$ ($\forall$$l$:IdLnk, ${\it tg}$:Id. $M_{1}$.dout($l$,${\it tg}$) $\subseteq\rho$ $M_{2}$.dout($l$,${\it tg}$))