TIBCO ActiveMatrix BusinessWorks(TM) Plug-in for SAP Solutions 8.x creates IDoc/RFCBAPI schema with references to other schema via relative path. The project must be saved in the workspace, otherwise the TIBCO BusinessStudio would not load the activity input/output correctly. In the situation project must be saved in the source control folder and workspace folder is at a different location, user could create a symbolic link (soft link) in the workspace. 

On Linux platform, please use 'ln -s' to create symbolic link, on Windows, please use 'mklink -d' to force create directory link.

An example on Windows:
source control folder is at d:\git
workspace folder is at c:\workspace
project folders are d:\git\sap and d:\git\sap.application
open 'cmd' with Administrator privilege
execute: mklink /d c:\workspace\sap d:\git\sap
execute: mklink /d c:\workspace\sap.application d:\git\sap.application
open TIBCO BusinessStudio.
go to File -> Import -> Existing Studio Project into workspace
browser to the c:\workspace
import the sap and sap.application.