\begin{tabbing}
ma\{\=${\it ds}$;\+
\\[0ex]${\it da}$;
\\[0ex]${\it init}$;
\\[0ex]${\it pre}$;
\\[0ex]${\it ef}$;
\\[0ex]${\it send}$;
\\[0ex]${\it frame}$;
\\[0ex]${\it sframe}$;
\\[0ex]${\it aframe}$;
\\[0ex]${\it bframe}$;
\\[0ex]${\it rframe}$;
\\[0ex]${\it prob}$\}
\-\\[0ex]$\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$$<$${\it ds}$, ${\it da}$, ${\it init}$, ${\it pre}$, ${\it ef}$, ${\it send}$, ${\it frame}$, ${\it sframe}$, ${\it aframe}$, ${\it bframe}$, ${\it rframe}$, ${\it prob}$, $\cdot>$
\end{tabbing}