$\forall$${\it es}$, ${\it es'}$:ES, $P$:(${\it es}$:ES$\rightarrow$E$\rightarrow\mathbb{P}$). (${\it es}$ = ${\it es'}$) $\Rightarrow$ ${\it es}$ $\equiv$ ${\it es'}$ mod ${\it es}$,$e$.$P$(${\it es}$,$e$)