\begin{tikzpicture}
\begin{umlseqdiag}
\umlactor[class=B]{b}
\umlentity[x=2, class=C]{c}
\umlboundary[x=4, class=D]{d}
\umlcontrol[x=0, y=-2.5, class=E]{e}
\umldatabase[x=2, y=-2.5, class=F]{f}
\umlmulti[x=4, y=-2.5, class=G]{g}
\end{umlseqdiag}
\end{tikzpicture}