Applying parameters' defaults to JCo / Adaptive RFC

Hi all,

Please, anyone with experience in both ABAP and WD Adaptive RFC, enlighten me regarding the following:

1. Input parameters for ABAP RFC function may have default value assigned. What values / expressions may be used here? From what I can found it is:

- constants ('character' or numeric)

- predefined data object SPACE + SY structure fields (SY-UNAME)

- Anything else???

2. I'm just wondering how SY-fields are applied by RFC client. Is there any way to get SY structure at client side? Simple "don't assign values" solution seems not to work... Or it is Adaptive RFC model specific...

3. Also it is unclear to me how user-specific SY-fields are working when user mapping involved for creating JCo connection.

Thanks in advance,

VS