$e$ $<$c ${\it e'}$ $\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$$e$ $\lambda$$e$,${\it e'}$. $e$ $<$loc ${\it e'}$ $\vee$ isrcv(kind(${\it e'}$)) \& $e$ $=$ sender(${\it e'}$)\^{}+ ${\it e'}$