\begin{frame} \frametitle{Weak Entity Sets} \weakentityexample \begin{block}{} A \emph{weak entity set} is an entity set without a primary key. \pause \begin{itemize} \item The existence of a weak entity set depends on the existence of an \emph{identifying entity set}. \pause \item There must be a total, one-to-many relationship set from the identifying entity set to the weak entity set. This \emph{identifying relationship} is depicted by a double diamond. \pause \item The $\disc{\text{\emph{discriminator}}}$ is a partial key, it distinguishes the\\[-.6ex] weak entity only in combination with the identifying entity. \pause \item Primary key of the weak entity set is a combination of the discriminator and primary key of the identifying entity set. \end{itemize} \end{block} \vspace{10cm} \end{frame}