The IOU Class in the Threading Package
Figure 4 shows the IOU class hierarchy. All but one of these classes are in the Interthread Communication package, which implements the framework for the IOU functionality. The hierarchy is duplicated here, because the piece that makes IOUs usable is the Threading package class RWTThreadEscrowImp. This class has the mechanisms for synchronizing multithread access to the result and blocking threads that have attempted to redeem the result before it has been supplied.
Figure 4 – IOU class hierarchy