rcv{-}from{-}on(${\it dE}$;${\it dL}$;${\it info}$;$e$;$l$;$r$) $\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$rcv?($r$) $\wedge_{2}$ eqof(${\it dE}$)($e$,sender($r$)) $\wedge_{2}$ eqof(${\it dL}$)($l$,link($r$))