SOAP to RFC sync scenario

Hello members:

we have a business scenario: SOAP to RFC sync

an external system (ABC) sends documentrequest thru XI SOAP adapter and makes an RFC call to a BAPI and gets back the resposne to the ABC system.we are handling 4 mappings. 1. request msg to a common msg 2. common msg to BAPI request3.bapi response to common msg 4. common msg to response msg(which is same as the req msg)

i have the request msg and common msg as external definitions. I did the following steps and wanted to

know if i am right.

1. there are no data type & msg type needed for this

2. 4 msg interfaces

i) document o/b sysnc

ii) document i/b sync

iii)common o/b sync

iiii) common i/b sync

3) 4 mappings

i) document to common

ii) common to bapi req

iii) bapi resp to common

iiii) common to req/response

4) 3 intf mappings

source intf********** target intf

i)document o/b common o/b uses mapping #1

ii)request :common i/b bapi i/b uses mapping #2

resposne:bapi i/b common i/b uses mapping #3

iii) common i/b document i/b uses mapping # 4

pls provide your inputs if my approach is rite? do i need to have 4 msg intefaces?has any made mappings where 4 mappings are involved ( without BPM)

Thanks in advance