rcv{-}from{-}on(${\it dE}$; ${\it dL}$; ${\it info}$; $e$; $l$; $r$)
\\[0ex]$\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$band(rcv?($r$); band((eqof(${\it dE}$)($e$,sender($r$))); (eqof(${\it dL}$)($l$,link($r$)))))