\documentclass[crop,tikz]{standalone}
\input{common-headers}
\input{sigles}

\begin{document}

\begin{tikzpicture}[%
  follow/.style={midway,sloped,above}]
  \node (mv)  at (0,0) {\model{M}{V}};
  \node (msv) at (2,1) {\model{M}{SV}};
  \node (ml)  at (2,-1) {\model{M}{L}};
  \node (msvl) at (4,0) {?};
  \node (msl) at (6,0) {\model{M}{SL}};

  \draw[-Stealth] (mv)  to node[follow] {\scriptsize abstraction} (msv);
  \draw[-Stealth] (mv)  to node[follow] {\scriptsize abstraction} (ml);
  
  \draw[-Stealth, dashed] (msv) to node[follow] {?} (msvl);
  \draw[-Stealth, dashed] (ml)  to node[follow] {?} (msvl);
  \draw[-Stealth, dashed] (msvl)  to node[follow] {?} (msl);
\end{tikzpicture}

\end{document}