\begin{tabbing}
ma{-}prob{-}da{-}dom($M$;$b$)
\\[0ex]$\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$\=(($\uparrow$$b$ $\in$ dom(($M$.2.2.2.2.2.2.2.2.2.2.2).1)) $\Rightarrow$ ($\uparrow$locl($b$) $\in$ dom(($M$.2).1)))\+
\\[0ex]\& ($b$ in dom($M$.pre) $\Rightarrow$ ($\uparrow$$b$ $\in$ dom($M$.prob)))
\-
\end{tabbing}