\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}