Roger Fischer from bitflux asked me about RDF implementations for digital libraries. Actually, there are almost none. This seems to be due to the fact that RDF is still an evolving technology, thus not used in production environments. Peter Gietz from DAASI pointed me to some interesting documents:
Search Mesh Topology and Visualisation
http://ilrt.org/discovery/2000/09/metamesh/
An Extensible Approach for Modeling Ontologies in RDF(S)
http://www.aifb.uni-karlsruhe.de/WBS/ama/publications/onto-rdfs_ekaw00.pdf
Sandro Groganz 