Inbound SUBMAS IDOC from external system

All,

We are implementing an interface between SAP EHS and an external formulation system.  The interface using SUBMAS IDOCs is bi-directional, meaning that data will be sent from the formulation system to SAP EHS and data will be sent from EHS to the formulation system, however not the same data points.  We also have intention to use the REPMAS IDOC, one way, to update the report status in the formulation system. We are converting, on the outbound side, the IDOC to the required XML for the formulation system within the middleware, and will be doing the same on the inbound side, converting the XML from the formulation system, to a SUBMAS IDOC to be posted within SAP.

Now, the inbound processing is expected to both create and update specifications, or update existing specifications.  It is on the inbound processing that my questions focus.

1. Has anyone had any experience with processing inbound SUBMAS IDOCs created from an external non-SAP system?
   • How did it work for you?
2. Which inbound processing function module was used for SUBMAS?
   • We are currently looking at BAPI_IDOC_INPUTP and BAPI_IDOC_INPUT1, both of which seems to do the same no matter which flags we set in the IDOC
3. Does any documentation exist on what the settings should be within the SUBMAS IDOC to process in specific ways? For instance:
   • Overwrite existing data (identifier or value assignment instance)
   • Append/add value assignment instance regardless of existing data
4. Do you perchance know how to separate the generation of the REPMAS from the generation of the DOCMAS? We have considered:
   • Filtering all sections of the IDOC except the header and ESTDH section.
     

Thank you in advance for any help that you can offer.