Stochastic programs must have two, or more, stages.  The first stage, stage 0, is the initial decision stage.  The second stage, stage 1, is a recourse decision stage which occurs after the stage 1 random variable values have been revealed.  Subsequent rounds of random variable revelations and recourse decisions are permitted but not required.  For more information on adding random variables and stages to an SP model, please refer to the Language Features for SP Models section in Chapter 14.