\begin{tabbing}
$\forall$\=${\it es}$:ES, $e_{1}$:E, $e_{2}$:\{$e$:E$\mid$ loc($e$) $=$ loc($e_{1}$) $\in$ Id \},\+
\\[0ex]$p$:(\{$e$:E$\mid$ loc($e$) $=$ loc($e_{1}$) $\in$ Id \}$\rightarrow$\{$e$:E$\mid$ loc($e$) $=$ loc($e_{1}$) $\in$ Id \}$\rightarrow$Prop).
\-\\[0ex][$e_{1}$,$e_{2}$]$\sim$([$a$,$b$].$p$($a$,$b$))+ $\in$ Prop
\end{tabbing}