$\forall$${\it es}$:ES, ${\it ff}$:FIFO. ${\it ff}$.Codes $\in$ $j$,$i$:${\it ff}$.C$\rightarrow$$e$:\{$x$:E$\mid$ ${\it ff}$.S($j$,$i$,$x$)\} $\rightarrow$state@loc($e$)$\rightarrow$${\it ff}$.T