\NewEnviron{stochasticModel}[1][1.5cm]{%
  \begin{tikzpicture}[node distance=#1,
                      thick,
                      action/.style={-,draw,sloped,above,pos=0.45},
                      transition/.style={->,draw,sloped,above,pos=0.5},
                      state/.style={circle,draw,minimum size=20pt},
                      dist/.style={circle,draw=black,fill=black,minimum size=4pt,inner sep=0pt}]
          \BODY
  \end{tikzpicture}
}