Oracle OTBI Cannot combine Person Real Time with another subject area?

Summary:

I cannot seem to combine the subject area "Workforce Management - Person Real Time" with any other subject area metric, that isn't "Worker"."Person Number". I ideally need to be able to do this within the OTBI for efficiency and ease of use. I know that I would be able to combine the data outside of OTBI - although this goes against the intended use of OTBI.

Content (required):

I have tried to combine e.g. the location name with a metric in the Person Real Time subject area e.g. marital status

Version (include the version you are using, if applicable):