\psset{linearc=.2}
\begin{psmatrix}[rowsep=3pt,colsep=-10pt]
[name=A]\psframebox{requirements}\\
&[name=B]\psframebox{design}\\
&&[name=C]\psframebox{coding}\\
&&&[name=D]\psframebox{testing}\\
&&&&[name=E]\psframebox{operations}
\psset{linearc=0,arrows=->,armA=0pt,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}