ProductDataResponse is
available for a request initiated by
PurchasingService.getProductData(java.util.Set).PurchaseResponse is
available for a purchase initiated by
PurchasingService.purchase(String).PurchaseUpdatesResponse is
available for a request initiated by
PurchasingService.getPurchaseUpdates(boolean).UserDataResponse is
available for a request initiated by
PurchasingService.getUserData().