$e$ sends to $i$ $\parallel$ $a$  $\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$$\forall$${\it e'}$@$i$. ($\uparrow$isrcv(${\it e'}$)) $\Rightarrow$ (sender(${\it e'}$) = $e$) $\Rightarrow$ val(${\it e'}$):valtype(${\it e'}$)$\parallel$$a$