\begin{frame}
  \frametitle{Intention Locks}
  
  \begin{goal}{}
    Databases use an additional type of locks: \emph{intention locks}.
    \begin{itemize}
      \item Lock mode \emph{intention share (IS)} 
      \item Lock mode \emph{intention exclusive (IX)} 
    \end{itemize}
    Before introducing S (or X) lock, first IS (or IX) locks on all coarser levels of granularity.
  \end{goal}
  \pause\medskip
  
  \begin{block}{Extended lock conflict matrix}
    \begin{center}
    \begin{tabular}{c|c c c c }
         & S & X & IS & IX\\
      \hline
      S  &   & \alert{x}  &    & \alert{x}  \\
      X  & \alert{x} & \alert{x} & \alert{x} & \alert{x} \\
      IS &   & \alert{x} &    &   \\
      IX & \alert{x} & \alert{x}  &    &   
    \end{tabular}
    \end{center}
  \end{block}
\end{frame}