OptionalroleHow the book's own XML refers to this entry, when it refers to it at all: book is the path
the book is opened from, absoluteUrl its 2021 cloud-URL companion.
Not derivable from type — the two can carry the SAME relationship type (measured on
task 40234, where a relative and an absolute externalLinkPath sit on one part). Absent for
an entry nothing points at, which is a real shape too: an xlPathMissing or
externalLinkLongPath rel rides along on the part without being referenced from it.
One
(relTypeUri, target)pair from the book part's own relationships — one place the source workbook may be found.Remarks
typeis the full relationship-type URI (not a shorthand) — it is what tells apart anexternalLinkPath, anxlExternalLinkPath/xlPathMissing(a bare name, not a URI), anexternalLinkLongPath, and an xxl21alternateUrlsentry. Emitting one under a hard-coded rel type would silently rewrite what the source file said.