After reading the spec it was still a bit unclear for me and it has an additional note:
Note: Additional members may be specified for links objects and link objects in the future.
So I'm assuming that
related attributes are the only 2 attributes allowed inside Relationship
Links. This Question also confirms it.
Then I have still further questions:
Q1: Presence of
related are XOR? Either one of them can appear in
Links but not at the same time, right?
Q2: Are the URL values for both attributes the same for a relationship Link object? Or where is the difference between those?