existse{-}between1(${\it es}$;$e_{1}$;$e_{2}$;$e$.$P$($e$))
\\[0ex]$\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$$\exists$$e$:es{-}E(${\it es}$). es{-}le(${\it es}$;$e_{1}$;$e$) \& es{-}locl(${\it es}$; $e$; $e_{2}$) \& $P$($e$)