LIBRIS, the Swedish Union Catalogue, has for some time now been available as Linked Data. Examples, of which some may hurt your eye if looked at in a HTML-browser; never fear, in time they will become beautiful, and might even include a squiggly animation.
The Difference Engine: http://libris.kb.se/resource/bib/5060570
Subject Heading ”Mödrar” (Mothers): http://libris.kb.se/resource/auth/154863
August Strindberg: http://libris.kb.se/resource/auth/94541
The Royal Library: http://libris.kb.se/resource/library/S
In a terminal window you can use curl to see the content negotioation in action:
curl --include --location --header accept:text/rdf+n3 http://libris.kb.se/resource/bib/5060570
We have used a mix of ontologies (FOAF, SKOS, Bibliontology, …), focusing on availability first rather than perfect representation of the underlying MARC-record. That comes later. The RDF also exposes some parts of our FRBR-algorithm, showing links between records believed to belong to the same work.
What we are working on right now is creating links to external datasets such as DBPedia/Wikipedia and between our own subject headings and to LCSH. This is pretty easily done once you have the data in RDF by the way.
As this is a work in (hopefully constant) progress, any input is appreciated. I will try to go into more detail later, until then I leave you with this picture.