effective($e$) $\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$$\exists$${\it e'}$:E(${\it Sys}$). $\exists$${\it e''}$:E(${\it Out}$). ($e$ is $f$$\ast$(${\it e'}$) \& ${\it e'}$ $\leq$loc ${\it e''}$ )