$\forall$${\it es}$:ES, $A$:Type, $X$:AbsInterface($A$ List), $e$:E($X$).
\\[0ex]es{-}interface{-}history(${\it es}$;$X$;$e$)
\\[0ex]=
\\[0ex]if $e$ $\in_{b}$ prior($X$) then es{-}interface{-}history(${\it es}$;$X$;prior($X$)($e$)) @ $X$($e$) else $X$($e$) fi 
\\[0ex]$\in$ ($A$ List)