@kupsch wrote:

A related location should say what is related to with a relatedTo property that is a URI (a sarif scheme URI relative to theResult). This is necessary as a tool may produce a relatedLocation that has its own related location, for instance, an error in foo.h may have a related location to say it was included from bar.h which was included in baz.c. Also since there may also be multiple locations, they may each have unique related locations.