$\forall$$T$:Type, $w$:World.
\\[0ex]FairFifo
\\[0ex]$\Rightarrow$ ($\forall$$e$:E, $x$:Id. (vartype(loc($e$);$x$) $\subseteq$r $T$) $\Rightarrow$ (state\_when($e$)($x$) = ($x$ when $e$) $\in$ $\mathbb{Q}\rightarrow$$T$))