[mathnmusic]

I have been dealing with the same problem for curating resources at https://learnawesome.org. Projects like Openlibrary do collect unique identifiers for _books_, but for everything else, it mostly takes manual effort. For example, I collect talks/podcasts by the author where they discuss ideas from their books. Then there are summaries written by others.

[dredmorbius]

There's a lot of work toward this in library space, though it takes some adaptation to new media formats. Paul Otlet worked in a paper-only medium in the early 20th century but also has some excellent thinking. His books are now seeing translation from French. The Internet Archive and Library of Congress are also doing a lot of relevant work, see the WARC format as an example.

What's particularly relevant now are ephemeral and/or continuously updated online content --- and not just the WWW (http/https), but other protocols (ftp, gemini, ipfs, torrents, ...), as well as apps.

A working truism I developed was that "identity is search that produces a single result". So if you can come up with something that uniquely identifies a work, then that can be a working identifier. I typically focus on what can be reasonably assessed of author, title, publication date, publisher (traditional, website/domain), and failing that, descriptive text. Remember that originally titles were simply the introductory lines of works (a practice that remains used in some cases, e.g., the names of church masses or prayers, e.g., "Kyrie Eleison").

The Superintendent of Documents (SuDoc) Classification Scheme (used by the US goverment and GAO) and operates by agency, type of publication, and further divisions, as well as date/year. https://www.fdlp.gov/about-fdlp/22-services/929-sudoc-classi...