Check out z39.50, you can use it to search and pull data from most national and university library catalogs. But also be prepared for some code archaeology along the way, as the protocol is around 50 years old.

https://en.wikipedia.org/wiki/Z39.50 https://z-brary.com/ https://github.com/asl2/PyZ3950/blob/master/PyZ3950/zoom.py

Depending on what you're looking for, a _lot_ more is being published by the Library of Congress as Linked Data nowadays, including LoC classification and subject headings. Check out https://id.loc.gov/.

[delayed]

https://id.loc.gov/download/ offers bulk downloads of many of the vocabularies, including the subject headings. In addition, individual records of various types can be search for.

Thanks.

That seems to have Subject Headings, but not the Classification, unless I'm blind (a fairly high likelihood).

I've spent quite some time poking around the LoC website over the years without finding anything more accessible than the PDFs of the Library of Congress Classification. Are you aware of that being generally available?

Near as I can tell, the best that's available is starting with the class(es) you want (e.g., https://id.loc.gov/authorities/classification/H.html for social sciences) and crawling recursively to grab whatever serialization of the RDF you want to consume. There's no SPARQL endpoint for id.loc.gov, alas, but it beats resorting to the PDFs.

Thanks.