Join two different Subject areas - Workforce Learning - Learning Management real time and Workforce

Summary

I am facing error when I tried joining two different subject areas (Learning and Person)

Content

In OTBI, I cannot able to Join two different Subject areas -  Workforce Learning - Learning Management real time and Workforce Management - Person Realtime..

Getting error in Results when I try to add the person subject area

Attached the XML

Please advice how do I join these subject areas, I am looking for a external identifier field from the person folder