\begin{frame} \frametitle{Aggregation} Consider the \textit{works-on} relation we have seen before. \mpause[1]{ \begin{goal}{} We now want to express that a task performed by an employee might have a manager assigned to it. \end{goal} } \mpause{ \begin{itemize} \item ER model has \alert{no relations between relations} \end{itemize} } \begin{exampleblock}{} \begin{center}\vspace{-4ex} \scalebox{.9}{ \begin{tikzpicture}[every edge/.style={link}] \node[entity] (employee) {employee}; \node[entity,right of=employee, node distance=6cm] (branch) {branch}; \node[entity,right of=employee, node distance=3cm,yshift=2cm] (job) {job}; \node[relationship,scale=.9,aspect=1.3] (works-on) at ($(employee)!.5!(branch)$) {works-on} edge (employee) edge (branch) edge (job); \mpause[1]{ \node[entity,above of=employee, node distance=2cm,xshift=-2.5cm] (manager) {manager}; \node[relationship,scale=.9,aspect=1.3] (manages) at ($(manager)+(2.5cm,0cm)$) {manages}; \draw (manages) to (manager); \begin{scope}[thick] \mpause[3]{ \draw (manages) to (employee); \draw (manages) to[out=45,in=90,looseness=1] (branch); \draw (manages) to (job); } \end{scope} } \end{tikzpicture}} \end{center} \end{exampleblock} \end{frame}