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\begin{frame}
  \frametitle{Recursive Associations}

  The correct way is to use a \emph{recursive association}:
  \begin{center}\vspace{-2ex}
  \begin{tikzpicture}
  \umlclass{employee}{ 
    +id \\
    +name \\
    +jobTitle \\
    +payGrade 
    }{ 
    }
  \umlassoc[arg1=0..*,pos1=0.1,arg2=0..1,pos2=.9,name=assoc, recursive=-30|30|3cm]{employee}{employee} 
  \node [bo=assoc-1,rotate=90] {$\triangleleft$ supervises$\quad$};
  \node [bo=assoc-1,rotate=90,yshift=-5mm] {supervised by$\triangleright$};
  \end{tikzpicture} 
  \end{center}\vspace{-2ex}
  \pause
  
  \begin{goal}{}
    A \emph{recursive association} translates to a foreign key that refers to the same table.
  \end{goal}
  
  \centering{\small\ttfamily
    \colorbox{rellight}{%
      \begin{tabular}[t]{|r|r|r|r|r|}
        \multicolumn{5}{c}{employee}        \\ \hline
        \hd{\key{id}} & \hd{name} & \hd{jobTitle}& \hd{payGrade} & \hd{supervisedBy$\to$id} \\ \hline 
        1 & James & \ldots & \ldots & 2  \\
        2 & Harrison & \ldots & \ldots & null \\
        \hline
      \end{tabular}%
    }}
\end{frame}