\begin{tabbing}
w{-}index($w$; $e$)
\\[0ex]$\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$\=$\parallel$w{-}rcvs($w$; lnk(w{-}ekind($w$; $e$)); w{-}time($w$; $e$))$\parallel$ \+
\\[0ex]{-} $\parallel$w{-}snds($w$; lnk(w{-}ekind($w$; $e$)); w{-}time($w$; w{-}sender($w$; $e$)))$\parallel$
\-
\end{tabbing}