\begin{xy}
 \xyWARMprocessMoEPS{\Fname a}{\grExt}
 \xyMarkedImport{\Fname a}
 \xyMarkedPos{x}*+!RD{x}
 \xyMarkedPos{y}*+!UL{y}
 \xyMarkedPos{z}*+!RD{z}
 \xyMarkedPos{P}*+!RD{P}
 \xyMarkedPos{Q}*+!UR{Q}
 \xyMarkedPos{phi}*+!UL{\varphi}
 \xyMarkedPos{theta}*+!DR{\theta(x,y,a)}
\end{xy}