\begin{frame}
  \frametitle{Fourth Normal Form}
 
  \begin{exampleblock}{}
    The relation
    $$
    \sql{Knowledge(\underline{employee}, \underline{programmingLanguage}, \underline{dbms})}
    $$
    is an example of a relation that is in BCNF, but not in 4NF.
    \medskip
    
    The relation has no non-trivial FDs.
  \end{exampleblock}
  
\end{frame}