ider the following state configuration:</p>

  <p><img alt="A" src="A.gif" border="0" width="230" height="170"></p>

  <p>Both states define entry actions (x() and y()). Whenever state A becomes
  active, a call to x() will immediately be followed by a call to y(). y()
  could depend on the side-effects of x(). Therefore, executing y() does not
  make sense if x() fails. This is not an esoteric corner case but happens in
  every-day state machines all the time. For example, x() could acquire
  memory the co