User Mapping

Hi ,

I am developing a web dynpro abap application in ECC6 which access some FM in ECC6. Their is no problem in creatng the ivew for this application in EP and everything goes fine. For user authentication we have SSO between EP and ECC6. Now we abt to use a FM in web dynpro application(ECC6) which resides in another sap system 4.6. Now to access the FM from 4.6 do we need the same user id as in ECC6. I mean.

Portal user id = XXX,

ECC6 user id = XXX,

4.6 user id = ???.

Because of sso we have same user id XXX between portal and ECC6. If we have to get data from 4.6 then their should be same user id in 4.6? or can the user id be different (say YYY).

Does i am making sense Or is any other way of getting done,

RK