$\forall$${\it the\_w}$:World, $e$, ${\it e'}$:E. FairFifo $\Rightarrow$ loc($e$) $=$ loc(${\it e'}$) $\in$ Id $\Rightarrow$ ($e$ $<$c ${\it e'}$ $\Leftrightarrow$ time($e$)$<$time(${\it e'}$))