This process involves three BOs in total.
1) Origin (CustomBO): Trigger point of creation
2) Proxy (CustomBO): Which has same structure as of std. SI BO and will have all elements that are needed to be filled.
3) SupplierInvoice (StandardBO): You don't need to explicitly create an XBO of this but you will see what you can do with this.
- Wherever(Origin BO's actions/events) you are writing code now to create SI, you should use that action file to write code for creating instances in your Proxy BO.
- As there will be an A2A(which is why you maintained same structure as of SI BO) setup between Proxy BO and SupplierInvoice BO, as soon as Proxy BO's instance gets created by Origin BO, it will automatically trigger an A2A call.
- You can check this sequence in debugging mode.
By using this approach, you should have full understanding of how A2A behaves. If there are any duplicate calls that might happen from your Origin BO, you should know how to handle them etc..