\begin{sequencediagram}
    \newthread{actor}{Actor}{}
    \newinst[4]{concordia}{:Concordia}{}
    \newinst[1]{eth}{:Ethereum}{}
    \newinst[2]{orbit}{:OrbitDb}{}

    \begin{call}{actor}{Modify post}{concordia}{Post modification form}
    \end{call}

    \begin{call}{actor}{Submit}{concordia}{Updated topic page}

        \begin{call}{concordia}{Save modified post information}{orbit}{}
        \end{call}

    \end{call}
\end{sequencediagram}