\begin{frame}
  \frametitle{Cardinality Limits}

  \begin{goal}{}
    \emph{Cardinality limits} express the number of entities
    to which another entity can be associated via a relationship set.
  \end{goal}
  \medskip
  
  There are many different notations. \emph{We use the UML notation!}
  \begin{block}{}
  \begin{center}
  \begin{tikzpicture}[every edge/.style={link},node distance=22mm,>=triangle 45,inner sep=.5mm]
    \begin{scope}
      \node[relationship] (R) {R};
      \node (l) [left of=R,entity,minimum size=4mm] {A}; \draw (R) -- node[above,pos=.6] {$M_1\sldots M_2$} (l); 
      \node (r) [right of=R,entity,minimum size=4mm] {B}; \draw (R) -- node[above,pos=.6] {$N_1\sldots N_2$} (r);
    \end{scope}
  \end{tikzpicture}
  \end{center}\vspace{-3mm}
  
  \begin{itemize}
    \item Every entity $a$ from $A$ is connected to \\
          at least $N_1$, and at most $N_2$ entities in $B$.
      \smallskip
    \item Every entity $b$ from $B$ is connected to \\
          at least $M_1$, and at most $M_2$ entities in $A$.
  \end{itemize}
  \end{block}
  \begin{exampleblock}{Typical cardinality constraints}
    \begin{malign}
      &\text{$0\sldots 1$\;= zero or one} && \text{$0\sldots *$\;= any number} \\
      &\text{$1\sldots 1$\;= precisely one} && \text{$1\sldots *$\;= at least one}
    \end{malign}
  \end{exampleblock}
\end{frame}