
%%% outline
%-------------------------------------------------------------------------

\begin{tikzpicture}

{\large
\node [anchor=west,minimum height=3em,inner sep=2pt] (eq11) at (0,0) {max};
\node [anchor=west,inner sep=2pt] (eq12) at ([xshift=2pt]eq11.east) {$\Big( \frac{\epsilon}{(l+1)^{m}} \prod\limits_{j=1}^{m} \sum\limits_{i=0}^{l}$};
\node [anchor=west,inner sep=2pt] (eq13) at (eq12.east) {$f(s_j|t_i)$};
\node [anchor=west,inner sep=2pt] (eq14) at ([yshift=0.2em]eq13.east) {$\Big)$};

\node [anchor=north west,minimum height=1.8em,inner sep=2pt] (eq21) at ([yshift=-0.5em]eq11.south west) {s.t.};
\node [anchor=west] (eq22) at ([xshift=0.5em,yshift=-0.1em]eq21.east) {\normalsize{for each word $t_y$}:};
\node [anchor=west] (eq23) at ([xshift=0.1em,yshift=-0.0em]eq22.east) {$\sum_{s_x} f(s_x|t_y) = 1$};

{
\node [anchor=west,minimum height=3em,inner sep=2pt,fill=green!20] (eq11) at (0,0) {max};
\node [anchor=west,draw,thin,ublue,inner sep=2pt,fill=blue!20] (eq13) at (eq12.east) {\black{$f(s_j|t_i)$}};

\node [anchor=north west,minimum height=1.8em,inner sep=2pt,fill=purple!20] (eq21) at ([yshift=-0.5em]eq11.south west) {s.t.};
\node [anchor=west,fill=orange!20] (eq23) at ([xshift=0.1em,yshift=-0.0em]eq22.east) {$\sum_{s_x} f(s_x|t_y) = 1$};
}

\begin{pgfonlayer}{background}
{
\node[rectangle,red,inner sep=0pt,fill=red!20] [fit = (eq12) (eq13) (eq14)] (eq1full) (eq1obj) {};
}
\end{pgfonlayer}
}

{
\node [anchor=west,draw,fill=green!20] (label1) at ([xshift=-2em,yshift=3em]eq11.north west) {最大化函数};
\node [anchor=west,draw,fill=red!20] (label2) at ([xshift=4em]label1.east) {目标函数};
\node [anchor=west,draw,fill=blue!20] (label3) at ([xshift=4em]label2.east) {参数};

\node [anchor=west,draw,fill=purple!20] (label4) at ([xshift=-2em,yshift=-2.5em]eq21.south west) {subject to=满足...约束};
\node [anchor=west,draw,fill=orange!20] (label5) at ([xshift=3em]label4.east) {翻译概率归一化约束条件};


\draw [<-,thick] ([xshift=-2em]label1.south) .. controls +(south:2em) and +(north:2em) .. (eq11.north);
\draw [<-,thick] ([xshift=-0em]label2.south) .. controls +(south:1.7em) and +(north:1.7em) .. (eq1obj.north);
\draw [<-,thick] ([xshift=-0em]label3.south) .. controls +(south:2.5em) and +(north:2.5em) .. (eq13.north);
\draw [<-,thick] ([xshift=2em]label4.north) .. controls +(north:1.5em) and +(south:1.5em) .. (eq21.south);
\draw [<-,thick] ([xshift=0em]label5.north) .. controls +(north:1.0em) and +(south:1.0em) .. (eq23.south);
}

\end{tikzpicture}



