\begin{frame}
  \frametitle{Introduction}
  
  \begin{block}{Recall the Decomposition Theorem}
    The split of relations is \emph{guaranteed to be lossless} if the
    intersection (the shared set attributes) of the attributes of the new tables is a key of at least one of them.
  \end{block}
  \pause
  
  \begin{alertblock}{}
  The condition in the decomposition theorem is only
  \begin{itemize}
  \item \emph{sufficient} (it guarantees losslessness),
  \item but \emph{not necessary} (a decomposition might be lossless
  even if the condition is not satisfied).
  \end{itemize}
  \end{alertblock}
  \bigskip
  \pause
  
  \begin{goal}{}
    \emph{Multivalued dependencies (MVDs)} are constraints that
    give a \emph{necessary and sufficient} condition for lossless decomposition   
  \end{goal}
  MVDs lead to the \emph{Fourth Normal Form (4NF)}.
\end{frame}