The way you can try to figure this out is to create a separate project and scaffold WebFlow from the embedded Derby database, then take a look at the generated code. The scaffolded webflow app uses a sub-flow if you have related tables.
Scaffold using these steps:
1. Create new Web Project
2. Right-click and select MyEclipse > Scaffold Spring Crud Application.
3. Select Database Schema and press next.
4. Select MyEclipse Derby and press next.
5. Select the Classiccars schema and select the Product and Orderdetail tables, then press next.
6. Select Product as the parent
7. Enter a package name and press next.
8. select Spring Web Flow and press Finish.
The Orderdetails table will be a subflow in the scaffolded app.
If you scaffold as suggested, you’ll find a subflow-state in the manageproducts.xml
<subflow-state id="manageorderdetailss" subflow="manageproductorderdetailss">
The id of the subflow is manageorderdetailss and it references the manageproductorderdetailss subflow. I believe that it is matching the filename of the subflow.