type BType      is union Empty | Full end

process Pre(&Stored, &Delayed : FailureType, S : BType, &env : Flows) is
   states s0
   from s0 select
      on (Stored != env.I and S = Empty); wait [0,0]; Stored := I; ...
   [] on (S = Full); wait [a,b]; Delayed := Stored; S := Empty; ...
   end