\usepackage {pstricks,pst-node}
\psset{framearc=.2}
\begin{psmatrix}[rowsep=1cm,colsep=-10pt]
[name=A]\psframebox{requirements}\\
&[name=B]\psframebox{design}\\
&&[name=C]\psframebox{coding}\\
&&&[name=D]\psframebox{testing}\\
&&&&[name=E]\psframebox{operations}
\psset{arrows=->,armA=0,angleB=90}
\ncangle{A}{B} \ncangle{B}{C}
\ncangle{C}{D} \ncangle{D}{E}
\psset{angleB=-90,angleA=180}
\ncangle{B}{A} \ncangle{C}{B}
\ncangle{D}{C} \ncangle{E}{D}
\end{psmatrix}
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