graph

graph.tex

\documentclass{standalone}
\usepackage{etex}
\usepackage{metalogo}
\usepackage{tikz}

\def\pTeX{p\TeX}
\def\epTeX{$\varepsilon$-\pTeX}
\def\upTeX{u\pTeX}
\def\eupTeX{$\varepsilon$-\upTeX}
\def\pdfTeX{\lower 2pt\hbox{pdf}\TeX}

\begin{document}
\begin{tikzpicture}[scale=1,
	block/.style = {rectangle, draw=black, thick, text width=5em, align=center, rounded corners, minimum height=2em}]

	\draw (0, 0) node[block] (A) {\TeX};
	\draw (2.5, -1.5) node[block] (B) {\eTeX};
	\draw (2.5, 1.5) node[block] (C) {\pTeX};

	\draw[->, very thick, blue] (A) -- (B);
	\draw[->, very thick, blue] (A) -- (C);

	\draw (2.5, 0) node[block] (D) {\epTeX};

	\draw[->, very thick, blue] (B) -- (D);
	\draw[->, very thick, blue] (C) -- (D);

	\draw (5, 1.5) node[block] (E) {\upTeX};
	\draw (5, 0) node[block] (F) {\eupTeX};

	\draw[->, very thick, blue] (C) -- (E);
	\draw[->, very thick, blue] (B) -- (F);
	\draw[->, very thick, blue] (E) -- (F);

	\draw (5, -1.5) node[block] (G) {\XeTeX};

	\draw[->, very thick, blue] (B) -- (G);

	\draw (2.5, -3) node[block] (H) {\pdfTeX};

	\draw[->, very thick, blue] (B) -- (H);

	\draw (5, -3) node[block] (I) {\LuaTeX};

	\draw[->, very thick, blue] (H) -- (I);
\end{tikzpicture}
\end{document}