\begin{frame}
  \frametitle{Examples}
  
  \begin{goal}{}
    In the ER model, the solution is the ``same'' as in the
    relational model: we have to \emph{split} the entity set.
  \end{goal}
  \medskip
  \pause
  
  \begin{exampleblock}{ER entity split}
    In this case, the instructor is an independent entity:
    \begin{tcenter}
      \scalebox{.9}{
      \begin{tikzpicture}[every edge/.style={link}]
        \node[entity] (customer) {Courses};
        \node[attribute] [above left of=customer,node distance=1.7cm,shift={(-7mm,-3mm)}] {\key{courseNr}} edge (customer);
        \node[attribute] [above of=customer,node distance=1.3cm] {title} edge (customer);

        \node[entity,xshift=70mm] (ins) {Instructors};
        \node[attribute] [above of=ins,node distance=1.1cm] {\key{instructor}} edge (ins);
        \node[attribute] [below left of=ins,node distance=1.7cm] {phone} edge (ins);

        \node[relationship] at($(customer)!.5!(ins)$) {given\_by}
          edge node [pos=.7,above] {$1..1$} (ins)
          edge node [pos=.7,above] {$0..*$} (customer);
      \end{tikzpicture}
      }  
    \end{tcenter}
  \end{exampleblock}
\end{frame}