$\forall$$x$, $y$:Id, $k$:Knd, $A$, $B$, $T$:Type, $f$:($A$$\rightarrow$$B$$\rightarrow$$T$$\rightarrow$$A$).
\\[0ex]$\neg$$y$ $=$ $x$ $\Rightarrow$ ma{-}single{-}effect1($x$;$A$;$y$;$B$;$k$;$T$;$f$) $\in$ MsgA