\begin{frame}
  \frametitle{IS-A, `Inheritance'}
  
  \vspace{-.5ex}
  \begin{goal}{\emph{Membership} constraints}
      \begin{itemize}
        \item 
          \begin{minipage}[t]{.66\textwidth}
          \emph{value-based}: assigns an entity to a specific subclass based on attribute values\\
          \hint{e.g. a \textit{person} of age $\ge$ 18 is an \textit{adult}}
          \end{minipage}~%
          \begin{minipage}[t]{.25\textwidth}\vspace{-3ex}
          \hspace{1cm}\scalebox{.9}{{\small%
          \begin{tikzpicture}[baseline=0ex,every edge/.style={link},node distance=12mm,>=triangle 45]
            \node[isa,scale=.7] (R) {ISA};
            \node (l) [above of=R,node distance=9mm] {}; \draw [=] (R) -- (l); 
            \node (r) [below of=R,node distance=7mm] {}; \draw [-] (R) -- node[right,align=center,pos=.9] {\textit{age}\\[-.5ex] $\ge$ 18} (r);
          \end{tikzpicture}%
          }}
          \end{minipage}\vspace{-0ex}
        \item default is \emph{user-defined}: manual assignment to subclasses
      \end{itemize}    
  \end{goal}
  \pause

  \vspace{-.75ex}
  \begin{goal}{\emph{Disjointness} constraints}
    \begin{itemize}
      \item 
        \begin{minipage}[t]{.66\textwidth}
        \emph{disjoint}: an entity can belong to at most one subclass; 
        \hint{e.g. a \textit{fruit} can be an \textit{apple} or a \textit{pear}, but not both}
        \end{minipage}~%
        \begin{minipage}[t]{.25\textwidth}\vspace{-3ex}
        \hspace{.8cm}\scalebox{.9}{{\small%
        \begin{tikzpicture}[baseline=0ex,every edge/.style={link},node distance=12mm,>=triangle 45]
          \node[isa,scale=.7] (R) {ISA};
          \node (l) [above of=R,node distance=9mm] {}; \draw [=] (R) -- (l); 
          \node (r) [below of=R,node distance=7mm] {}; \draw [-] (R) -- node[right,pos=.7] {disjoint} (r);
        \end{tikzpicture}%
        }}
        \end{minipage}
      \item default is \emph{overlapping}: can belong to multiple subclasses
    \end{itemize}
  \end{goal}
  \pause
  
  \vspace{-.75ex}
  \begin{goal}{\emph{Completeness} constraints}
    \begin{itemize}
      \item 
        \begin{minipage}[t]{.66\textwidth}
        \emph{total specialisation (generalisation)} constraint:
        each superclass entity must belong to a subclass;
        \hint{e.g. a \textit{person} is either a \textit{minor} or an \textit{adult}}
        \end{minipage}~%
        \begin{minipage}[t]{.25\textwidth}\vspace{-3ex}
        \hspace{1cm}\scalebox{.9}{{\small%
        \begin{tikzpicture}[baseline=0ex,every edge/.style={link},node distance=12mm,>=triangle 45]
          \node[isa,scale=.7] (R) {ISA};
          \node (l) [above of=R,node distance=9mm] {}; \draw [-,double,double distance=1] (R) -- (l); 
          \node (r) [below of=R,node distance=7mm] {}; \draw [-] (R) -- (r);
        \end{tikzpicture}%
        }}
        \end{minipage}
%         \vspace{.1ex}
%       \item default is \emph{partial specialisation (generalisation)}:
%         entities of the superclass may not belong to any subclass
    \end{itemize}
  \end{goal}
\end{frame}