Tardis:"Real world" versus "from the real world"

How do we distinguish between those things that exist in the real world and the Doctor Who universe versus those things that only exist in the real world? How do we categorise Marco Polo — a real person who appeared in Doctor Who — versus Philip Hinchcliffe — a real person who does not exist in the DWU?

It's a hard question, especially because Doctor Who delights in exploring real world history. What we've come up with is a nomenclature that's consistently applied across our articles.


 * A thing that only exists in the real world belongs to "real world ". Hence real world musicians are those musicians who have never been a part of the DWU, like Athlete, the group that provided the extra-diegetic song "Chances" for Vincent and the Doctor.   Since "Chances" couldn't be heard by the actors, "Athlete" aren't a part of the DWU, but rather a part of the extended crew that made Doctor Who.
 * A thing that exists both in the real world and the DWU belongs to " from the real world". Hence musicians from the real world are those real musicians who have appeared in a DWU story.  So Paul McCartney is a "musician from the real world", since he appeared in The Chase and other stories.