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