\begin{frame}
  \frametitle{ISA to Relational Model}

  \isaexample
  \pause
  
  \vspace{-.5ex}
  \begin{goal}{Method 1: hierarchy of tables}
    \begin{itemize}
      \item a table for the higher-level entity set
      \item a table for each lover-level entity set;
        include primary key of higher-level entity set
        and local attributes
    \end{itemize}
     
  \end{goal}
  \vspace{-.5ex}
  
  \begin{center}
  {\footnotesize\ttfamily
    \parbox{.2\textwidth}{
    \colorbox{rellight}{%
      \begin{tabular}[t]{|r|r|}
        \multicolumn{2}{c}{Person}        \\ \hline
        \hd{\key{id}} & \hd{name} \\ \hline 
        1 & James \\
        2 & Jones \\
        \hline
      \end{tabular}%
    }}~\quad~%
    \parbox{.3\textwidth}{
    \colorbox{rellight}{%
      \begin{tabular}[t]{|r|r|}
        \multicolumn{2}{c}{Employee}        \\ \hline
        \hd{\key{id}$\;\to\;$Person} & \hd{salary} \\ \hline 
        1 & 4000 \\
        \hline
      \end{tabular}%
    }\\[.25ex]
    \colorbox{rellight}{%
      \begin{tabular}[t]{|r|r|}
        \multicolumn{2}{c}{Customer}        \\ \hline
        \hd{\key{id}$\;\to\;$Person} & \hd{credit-rating} \\ \hline 
        2 & 42 \\
        \hline
      \end{tabular}%
    }}
  }
  \end{center}
  \emph{Minor drawback:} requires accessing multiple tables.
  \vspace{10cm}
\end{frame}