%&tex
\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary {quotes,arrows.meta,graphs,graphdrawing} \usegdlibrary {layered}
\tikzset{nodes={text height=.7em, text width=2.7cm, align=center,
draw=black!20, thick, fill=white, font=\footnotesize},
>={Stealth[round,sep]}, rounded corners, semithick}

\begin{document}

\begin{tikzpicture}

\graph [layered layout, level distance=1.2cm, sibling sep=.5em, sibling distance=1.5cm, sweep crossing minimization] {
{"Design Method", "System Engineering"} -> "Design Plan";
{"Evaluation Plan", "Design Plan", "Subject of design"} -> "Case Study";
};
\end{tikzpicture}
\end{document}