$\forall$$A$:Type, ${\it eq}$:EqDecider($A$), $B$:($A$$\rightarrow$Type), $f$, $g$:$a$:$A$ fp$\rightarrow$ $B$($a$), $x$:$A$, $z$:$B$($x$).
\\[0ex]$f$ $\parallel$ $g$ $\Rightarrow$ $f$ $\oplus$ $g$($x$)?$z$ $=$ $g$($x$)?$f$($x$)?$z$ $\in$ $B$($x$)