latex-beamer: ambiguous highlighting with \setbeamercovered{transparent}

Question

I am having problems with the following piece of code:

\documentclass{beamer}
\setbeamercovered{transparent}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\begin{document}
\begin{frame}
\begin{itemize}
\item<alert@4-> a
\pause
\item b
\pause
\item c
\pause
\end{itemize}
\end{frame}
\end{document}

I want to have a,b and c highlighted one after one, and in the end alert the first item. Unfortunately on page one of the generated document b is already highlighted, although only a should be.

Here's an image of the first slide:

What did I do wrong?

Answer 1

\documentclass{beamer}
\setbeamercovered{transparent}

\begin{document}

\begin{frame}
\begin{itemize}
\item<1-|alert@4-> a
\item<2-> b
\item<3-> c
\end{itemize}
\end{frame}

\end{document}

Answer 2

Another alternative, just swap the alerted bullet list to display on the last slide.

\documentclass{beamer}
\setbeamercovered{transparent}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\begin{document}
\begin{frame}
  \begin{itemize}
    \begin{onlyenv}<1-3>
    \item a \pause
    \item b \pause
    \item c \pause
    \end{onlyenv}

    \begin{onlyenv}<4>
    \item<alert@4> a 
    \item b 
    \item c 
    \end{onlyenv}
  \end{itemize}
\end{frame}
\end{document}

Answer 3

Another example:

\documentclass{beamer}
\setbeamercovered{transparent}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\begin{document}
\begin{frame}
    \begin{itemize}
        \alert<4>{\item a}      
        \pause \item b
        \pause \item c
    \end{itemize}
\end{frame}
\end{document}