\begin{diagram}{Protocol type}{protocoltype}
\begin{mysyntdiag}
\lit*{objcprotocol}
\begin{stack}\\ 
\lit*{external}
\begin{stack}\\ \lit*{name} \synt{string\ constant}
 \end{stack}
 \end{stack}
 
\begin{stack}\\ heritage \end{stack}
\begin{stack}
\synt{protocol\ method\ list} 
\end{stack}
\lit*{end} 
\end{mysyntdiag}
\begin{mysyntdiag}
\synt{heritage} \lit*( 
  \begin{rep}[b] 
    \synt{protocol\ type\ identifier} \\
    \lit{,}
  \end{rep}
\lit* )
\end{mysyntdiag}
\begin{mysyntdiag}
  \synt{protocol\ method\ list} 
  \begin{rep}[b]
    \begin{stack}\\
    \lit*{required}\\
    \lit*{optional}
    \end{stack} 
    \begin{stack} 
      \synt{method\ definition} % \\
%      \synt{property\ definition}
    \end{stack} \\ 
  \end{rep} 
\end{mysyntdiag}
\end{diagram}