Am i the only one who feels that the database needs them? Was MusicBrainz lacking track lengths for the first decade of its existence?
It’s such a natural way to represent 1) order of works inside a book 2) relative size of works. Even for an e-book with lost layout and free flow of text it would be somewhat informative telling us the parts’ size proportions.
Of course to represent Work order inside a complex Work (when it’s not related to a particular Edition) the database may require another attribute, but that also can be read by a script when needed, saving a human editor from manually reordering when a new db entry is inserted somewhere in the middle.