Cross subject area - on which facts are they joined?

Content

Hi there

I have joined two subject areas 

- Expenses - Expense Transaction details real time
- Workforce Management - Work Relationship Real time

to get level 2 department from the Workforce management.

I think that I'm able to see that it's Person number from Workforce management SA and Employee Number from Expenses SA, that are joined... But I can't seem to find it documented anywhere...

I have issued the sql in the administration-part of OTBI and gotten the log on level 2... But it isn't obvious to me, which fact-columns are joined according to the log... 

I would think that there should be a where-clause somewhere, that says "where Employee Number = Person Number", but I cant find it...