\begin{tabbing}
constR\=\{\$x:ut2\}\+
\\[0ex]($T$; $c$; $i$)
\-\\[0ex]$\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$$\oplus$(@$i$ "\$x" initially $c$:$T$.@$i$ only events in nil change "\$x":$T$.nil)
\end{tabbing}