\begin{frame} \frametitle{Entity Sets} \begin{block}{} An \emph{entity} is an abstract object \begin{itemize} \item e.g.: specific person, company, event \end{itemize} \smallskip Entities have \emph{attributes} \begin{itemize} \item e.g.: people have names and addresses \end{itemize} \smallskip An \emph{entity set} is a collection of similar entities \begin{itemize} \item similar = sharing the same properties (attributes) \item e.g.: set of all persons, companies, trees, holidays \end{itemize} \end{block} \medskip \pause \begin{goal}{} \emph{Comparison with object-oriented programming:} \begin{talign} \text{entity $\approx$ object} && \text{entity set $\approx$ class} \end{talign} \pause Important difference: the \emph{ER model is static} \begin{itemize} \item models structure of the data, not the operations \item no methods/functions associated to entity sets \end{itemize} \end{goal} \end{frame}