I implementing a custom process type for BW process chains with ABAP OO and like to have an execution interface IF_RSPC_EXECUTE only because no variants are necessary. I read that this interface is the only required one but then I cannot add the process type to a chain. I got a message I:0000 and then E:0000 without any information about the reason. If I also implement IF_RSPC_MAINTAIN and IF_RSPC_GET_VARIANT for maintaining the variant then it works fine.
Is this a change in the SAP interface definition, perhaps an error or is it necessary to implement this interfaces also?