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\begin{frame}
\frametitle{Cardinality Limits: One-to-One}

\begin{center}\vspace{-1ex}
\begin{scope}
\node[relationship] (R) {R};
\node (l) [left of=R,entity,minimum size=4mm] {A}; \draw (R) -- node[above,pos=.6] {$0\sldots1$} (l);
\node (r) [right of=R,entity,minimum size=4mm] {B}; \draw (R) -- node[above,pos=.6] {$0\sldots1$} (r);

\begin{scope}[nodes={draw,rectangle,fill=green!20,minimum size=4mm,scale=.8}]
\foreach \i in {1,2,3,4,5,6} {
\node at (-12mm,-5mm*\i - 3mm) (a\i) {a\i};
\node at (12mm,-5mm*\i - 3mm) (b\i) {b\i};
}
\end{scope}

\begin{scope}[thick]
\draw (a1) to[out=0,in=180] (b1);
\draw (a2) to[out=0,in=180] (b3);
\draw (a4) to[out=0,in=180] (b6);
\draw (a5) to[out=0,in=180] (b4);
\end{scope}
\end{scope}

\begin{scope}[xshift=5cm]
\node[relationship] (R) {R};
\node (l) [left of=R,entity,minimum size=4mm] {A}; \draw (R) -- node[above,pos=.7] {$1\sldots 1$} (l);
\node (r) [right of=R,entity,minimum size=4mm] {B}; \draw (R) -- node[above,pos=.7] {$1\sldots 1$} (r);

\begin{scope}[nodes={draw,rectangle,fill=green!20,minimum size=4mm,scale=.8}]
\foreach \i in {1,2,3,4,5,6} {
\node at (-12mm,-5mm*\i - 3mm) (a\i) {a\i};
\node at (12mm,-5mm*\i - 3mm) (b\i) {b\i};
}
\end{scope}

\begin{scope}[thick]
\draw (a1) to[out=0,in=180] (b1);
\draw (a2) to[out=0,in=180] (b3);
\draw (a3) to[out=0,in=180] (b2);
\draw (a4) to[out=0,in=180] (b6);
\draw (a5) to[out=0,in=180] (b4);
\draw (a6) to[out=0,in=180] (b5);
\end{scope}
\end{scope}
\end{tikzpicture}\vspace{-.5ex}
\end{center}

\pause
\begin{goal}{}
Both are called \emph{one-to-one} relationship set.
\smallskip

For the diagram on the left we have:
\begin{itemize}
\item every $a$ in $A$ is connected to at most one (= $0$ or $1$) $b$ in $B$
\item every $b$ in $B$ is connected to at most one (= $0$ or $1$) $a$ in $A$
\end{itemize}

For the diagram on the right we have:
\begin{itemize}
\item every $a$ in $A$ is connected to precisely one $b$ in $B$
\item every $b$ in $B$ is connected to precisely one $a$ in $A$
\end{itemize}
\end{goal}
\vspace{10cm}
\end{frame}