\begin{figure}[h!]
\centering

\subfigure[First possible way to split $x@z$]{\label{seq_first_split}
\scalebox{0.7}{
\begin{tikzpicture}
    \node[draw,minimum height=3.8ex] (xa) { $\hspace{4em}xa\hspace{4em}$ };
    \node[draw,minimum height=3.8ex, right=-0.03em of xa] (xxa) { $\hspace{0.5em}x - xa\hspace{0.5em}$ };
    \node[draw,minimum height=3.8ex, right=-0.03em of xxa] (z) { $\hspace{21em}$ };

    \draw[decoration={brace,transform={yscale=3}},decorate]
           (xa.north west) -- ($(xxa.north east)+(0em,0em)$)
               node[midway, above=0.5em]{$x$};

    \draw[decoration={brace,transform={yscale=3}},decorate]
           (z.north west) -- ($(z.north east)+(0em,0em)$)
               node[midway, above=0.5em]{$z$};

    \draw[decoration={brace,transform={yscale=3}},decorate]
           ($(xa.north west)+(0em,3ex)$) -- ($(z.north east)+(0em,3ex)$)
               node[midway, above=0.8em]{$x @ z \in L_1 ;; L_2$};

    \draw[decoration={brace,transform={yscale=3}},decorate]
           ($(z.south east)+(0em,0ex)$) -- ($(xxa.south west)+(0em,0ex)$)
               node[midway, below=0.5em]{$(x - xa) @ z \in L_2$};

    \draw[decoration={brace,transform={yscale=3}},decorate]
           ($(xa.south east)+(0em,0ex)$) -- ($(xa.south west)+(0em,0ex)$)
               node[midway, below=0.5em]{$xa \in L_1$};
\end{tikzpicture}}}

\subfigure[Transferred structure corresponding to the first way of splitting]{\label{seq_trans_first_split}
\scalebox{0.7}{
\begin{tikzpicture}
    \node[draw,minimum height=3.8ex] (xa) { $\hspace{4em}ya\hspace{4em}$ };
    \node[draw,minimum height=3.8ex, right=-0.03em of xa] (xxa) { $\hspace{0.5em}y - ya\hspace{0.5em}$ };
    \node[draw,minimum height=3.8ex, right=-0.03em of xxa] (z) { $\hspace{21em}$ };

    \draw[decoration={brace,transform={yscale=3}},decorate]
           (xa.north west) -- ($(xxa.north east)+(0em,0em)$)
               node[midway, above=0.5em]{$y$};

    \draw[decoration={brace,transform={yscale=3}},decorate]
           (z.north west) -- ($(z.north east)+(0em,0em)$)
               node[midway, above=0.5em]{$z$};

    \draw[decoration={brace,transform={yscale=3}},decorate]
           ($(xa.north west)+(0em,3ex)$) -- ($(z.north east)+(0em,3ex)$)
               node[midway, above=0.8em]{$y @ z \in L_1 ;; L_2$};

    \draw[decoration={brace,transform={yscale=3}},decorate]
           ($(z.south east)+(0em,0ex)$) -- ($(xxa.south west)+(0em,0ex)$)
               node[midway, below=0.5em]{$(y - ya) @ z \in L_2$};

    \draw[decoration={brace,transform={yscale=3}},decorate]
           ($(xa.south east)+(0em,0ex)$) -- ($(xa.south west)+(0em,0ex)$)
               node[midway, below=0.5em]{$ya \in L_1$};
\end{tikzpicture}}}

\subfigure[The second possible way to split $x@z$]{\label{seq_snd_split}
\scalebox{0.7}{
\begin{tikzpicture}
    \node[draw,minimum height=3.8ex] (x) { $\hspace{6.5em}x\hspace{6.5em}$ };
    \node[draw,minimum height=3.8ex, right=-0.03em of x] (za) { $\hspace{2em}za\hspace{2em}$ };
    \node[draw,minimum height=3.8ex, right=-0.03em of za] (zza) { $\hspace{6.1em}z - za\hspace{6.1em}$  };

    \draw[decoration={brace,transform={yscale=3}},decorate]
           ($(za.north west)+(0em,0ex)$) -- ($(zza.north east)+(0em,0ex)$)
               node[midway, above=0.8em]{$z$};

    \draw[decoration={brace,transform={yscale=3}},decorate]
           ($(x.north west)+(0em,3ex)$) -- ($(zza.north east)+(0em,3ex)$)
               node[midway, above=0.8em]{$x @ z \in L_1 ;; L_2$};

    \draw[decoration={brace,transform={yscale=3}},decorate]
           ($(za.south east)+(0em,0ex)$) -- ($(x.south west)+(0em,0ex)$)
               node[midway, below=0.5em]{$x @ za \in L_1$};
\end{tikzpicture}}}


\subfigure[Transferred structure corresponding to the second way of splitting]{\label{seq_trans_snd_split}
\scalebox{0.7}{
\begin{tikzpicture}
    \node[draw,minimum height=3.8ex] (x) { $\hspace{6.5em}y\hspace{6.5em}$ };
    \node[draw,minimum height=3.8ex, right=-0.03em of x] (za) { $\hspace{2em}za\hspace{2em}$ };
    \node[draw,minimum height=3.8ex, right=-0.03em of za] (zza) { $\hspace{6.1em}z - za\hspace{6.1em}$  };

    \draw[decoration={brace,transform={yscale=3}},decorate]
           ($(za.north west)+(0em,0ex)$) -- ($(zza.north east)+(0em,0ex)$)
               node[midway, above=0.8em]{$z$};

    \draw[decoration={brace,transform={yscale=3}},decorate]
           ($(x.north west)+(0em,3ex)$) -- ($(zza.north east)+(0em,3ex)$)
               node[midway, above=0.8em]{$y @ z \in L_1 ;; L_2$};

    \draw[decoration={brace,transform={yscale=3}},decorate]
           ($(za.south east)+(0em,0ex)$) -- ($(x.south west)+(0em,0ex)$)
               node[midway, below=0.5em]{$y @ za \in L_1$};
\end{tikzpicture}}}

\caption{The case for $SEQ$}
\end{figure}