[Tex/LaTex] How to construct a waterfall model diagram by LaTeX in Beamer

Question

I need to construct a Waterfall model diagram like these:

Answer 1

An alternative to Gernot nice answer, in which is employed chains TikZ library and connection between nodes are establish in a loop:

\documentclass[tikz, margin=3mm]{standalone}
\usepackage{}
\usetikzlibrary{chains,positioning,shadows}

\begin{document}
    \begin{tikzpicture}[>=stealth,
    node distance = 3mm and 3mm,
      start chain = A going below right,
every node/.style = {draw, text width=24mm, minimum height=12mm, align=center,
                     inner sep=1mm, fill=white, drop shadow={fill=black},  on chain=A},
                        ]
\node {Requirements}; % A-1
\node {Design};
\node {Coding and unit test};
\node {System integration};
\node {Operation and maintenance};
%
\foreach \i [count=\j] in {2,...,5}
{
  \draw[->, thick] (A-\i) -| (A-\j);
  \draw[->, thick] (A-\j) -| (A-\i);
}
\end{tikzpicture}
\end{document}