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