As you probably know it is the basis of the service oriented architecture to use webservices for the communication amongst different components. Also if you create a environment with SAP BPM and SAP MDM webservices on MDM site are generated and consumed in SAP BPM.
During the implementation of this scenario we encountered the problem, that the webservice call from SAP BPM is successfully executed. Also on MDM site the calculation was successfully and in the SOA Logger the result was visible. But the result never went into SAP BPM.
The solution of the problem was pretty simple but really hard to find: SAP MDM webservice DO NOT support WSIL. WSIL is the generic webservice file in which all services of the server are listed and not only the specific ones for the single webservice. So we created a new provider system pointing to the WSDL of the service and added this provider system then in the application communication to the service group and it worked!