mar/graphics/approach.tex

%&tex
\documentclass{standalone}
\usepackage{tikz}
\usepackage{siltex}
\usetikzlibrary {arrows.meta,positioning} 
\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}[on grid,y=1.2cm,x=1.6cm]
    \node (dm) {RIDM};
    \node (a1)[right = 1 of dm, draw=none, fill=none] {};
    \node (se)[right = 2 of dm] {Systems Engineering};
    \node (dp)[below = 1 of a1] {Design Plan};
    \node (ep)[left  = 2 of dp] {Evaluation Protocol};
    \node (sd)[right = 2 of dp] {Subject of Design};
    \node (cs)[below = 1 of dp] {Case Study};
    \path[->] (dm) edge (dp)
              (se) edge (dp)
              (ep) edge (cs)
              (dp) edge (cs)
              (sd) edge (cs);
\end{tikzpicture}
\end{document}