are you looking for examples how library data is represented on the Semantic Web side? Just to name a few notable developments:
- Library of Congress Authorities' data sets, e.g. Subject Headings LCSH http://id.loc.gov/
(there are much more to mention)
These files are representations for the Semantic Web, they can be collected and used in tools for querying, or indexing, or creating links, mashups etc.
There are some visualizations like the "Linked Open Data cloud" of Richard Cyganiak and Anja Jentzsch that show e.g. GND, VIAF, LCSH as part of the Semantic Web
The main point is that many national libraries have already started offering their authority files via Semantic Web, because the reuse rate of this data, the validity, and the trust into the correctness of this kind of data is high. In the next years, library catalogs with title or holdings data are expected to link to those entities, and by doing this, library systems can adapt to RDF and Semantic Web services at their own preference and speed. Bibframe is of great help to proceed along that path.