\begin{tabbing}
component{-}compatible(${\it ds}$;${\it da}$;$T_{1}$;$T_{2}$;$C_{1}$;$C_{2}$)
\\[0ex]$\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$\=$\forall$$X_{1}$:Interface(${\it ds}$;${\it da}$;$T_{1}$), $X_{2}$:Interface(${\it ds}$;${\it da}$;$T_{2}$).\+
\\[0ex]scheme{-}compatible(($C_{1}$($X_{1}$)).1;($C_{2}$($X_{2}$)).1)
\-
\end{tabbing}