pred!($E$;${\it pred?}$;${\it info}$;$e$;${\it e'}$)
\\[0ex]$\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$$\neg$first(${\it pred?}$;${\it e'}$) \& $e$ $=$ pred(${\it pred?}$;${\it e'}$) $\in$ $E$ $\vee$ rcv?(${\it info}$;${\it e'}$) \& $e$ $=$ sender(${\it info}$;${\it e'}$) $\in$ $E$