\begin{frame} \frametitle{Cardinality Limits: Many-to-Many} \begin{center} \begin{tikzpicture}[every edge/.style={link},node distance=22mm,>=triangle 45] \begin{scope} \node[relationship] (R) {R}; \node (l) [left of=R,entity,minimum size=4mm] {A}; \draw (R) -- node[above,pos=.6] {$0\sldots *$} (l); \node (r) [right of=R,entity,minimum size=4mm] {B}; \draw (R) -- node[above,pos=.6] {$0\sldots *$} (r); \begin{scope}[nodes={draw,rectangle,fill=green!20,minimum size=4mm,scale=.8}] \foreach \i in {1,2,3,4,5,6,7} { \node at (-12mm,-5mm*\i - 4mm) (a\i) {a\i}; \node at (12mm,-5mm*\i - 4mm) (b\i) {b\i}; } \end{scope} \begin{scope}[thick] \draw (a1) to[out=0,in=180] (b1); \draw (a3) to[out=0,in=180] (b2); \draw (a4) to[out=0,in=180] (b3); \draw (a4) to[out=0,in=180] (b5); \draw (a4) to[out=0,in=180] (b6); \draw (a5) to[out=0,in=180] (b6); \draw (a6) to[out=0,in=180] (b6); \draw (a6) to[out=0,in=180] (b7); \end{scope} \end{scope} \end{tikzpicture}\vspace{-.5ex} \end{center} \begin{goal}{} This describes a \emph{many-to-many} relationship set: \begin{itemize} \item the entities may be connected arbitrarily \item every $a$ in $A$ can be linked to an arbitrary number of $B$'s \item every $b$ in $B$ can be linked to an arbitrary number of $A$'s \end{itemize} \end{goal} If the cardinalities are not given, the \emph{default is many-to-many}. \vspace{10cm} \end{frame}