hash(<dc:identifier>)- hashes are as long or short as you need them to be
- publication timestamp is in every ebook’s metadata, is almost guaranteed to be unique, monotonically increases, and has actual semantic meaning compared to an isbn or oclc
They don't need to. It'd be smart. It's not "arbitrary". It's fucking library science.
>hashes are as long or short as you need them to be
Hashes might uniquely identify a computer file, but they don't uniquely identify an edition/release of a published book. Some jackass on libgen decides to tweak a single byte, now it has a new hash... but it's not a new edition.
>publication timestamp is in every ebook’s metadata
As someone who takes a look at every internal opf file, no... they're not in every ebook.
You're suggesting I go to the extra trouble of doing a job they could do easily, when I can only do it poorly, and I don't know why... because the first person to respond was a dumbass and thought I was attacking him? I swear, 99% of humans are still monkeys.