$\forall$$w$:World.
\\[0ex]FairFifo $\Rightarrow$ ($\forall$$e$:E. state\_when($e$) = ($\lambda$$x$.s(loc($e$);time($e$)).$x$) $\in$ $x$:Id$\rightarrow\mathbb{Q}\rightarrow$vartype(loc($e$);$x$))