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\begin{frame}
  \frametitle{Transaction}
  
  \begin{goal}{}
    A \emph{transaction} is a list of actions.
    \medskip
    
    The \emph{actions} are
    \begin{itemize}
      \item reads (written \tread{O}) and
      \item writes (written \twrite{O})
    \end{itemize}
    of database objects O.
    \medskip
    
    Transactions end with \emph{Commit} or \emph{Abort}.\\
    \remark{%
      These are sometimes omitted if not relevant.
    }
  \end{goal}
  \medskip
    
  \begin{exampleblock}{Example Transaction}
    \begin{malign}
      T_1 \;:\; \tread{V}, \tread{Y}, \twrite{V}, \twrite{C}, \tcommit
    \end{malign}
  \end{exampleblock}
\end{frame}