帮助在 tikz 中绘制附图

Question

请帮忙用 tikz 画出这个图表。这种类型的图表应该包含多少层。问题是在下一层不使用分叉。谢谢

\documentclass[a4paper, 12pt]{article}
% Preamble

% Package used for input and output display.
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}

% Package used for diagram.
\usepackage{tikz}
\usetikzlibrary{trees}

% Page layout.
\usepackage[margin=2cm]{geometry}

% Begin document.
\begin{document}
% Preamble.


\begin{figure}
\centering
\begin{tikzpicture}[
      thesis/.style={draw,rectangle,fill=white,text width=5 em, minimum height=5mm},
      parent/.style={draw,rectangle,fill=white,rounded corners=5, text width=5.5em, text centered, minimum height=10mm, node distance=7em, minimum width=8em},
every node/.style={draw,rectangle,fill=white,text width=2.7em, text centered, minimum height=6mm,node distance=1em},
level1/.style ={level distance=1.8cm},]

 
\node[parent]{\textbf{Data}} [edge from parent fork down] [sibling distance=3cm]
     child[level1] {node[thesis] {Data1}}
     child[level1]  {node[thesis] {Data2}}
     child[level1]  {node[thesis] {Data3}}
     child[level1]  {node[thesis] {Data4}}
     child[level1]  {node[thesis] {Data5}}
     child[level1]  {node[thesis] {Data6}}
;

\end{tikzpicture}
\end{figure}
\end{document}