INSPIRE is (contains?) a set of standard for geo-data/meta-data exchange that the EU suggests the member countries should implement. Builds on top of GML etc.
"GeoNetwork is a catalog application to manage spatially referenced resources. It provides powerful metadata editing and search functions as well as an embedded interactive web map viewer. It is currently used in numerous Spatial Data Infrastructure initiatives across the world."
Implements INSPIRE - integrates AGROVOC?
geometry2rdf is a library for generating RDF files for geometrical information (which could be available in GML or WKT). The GML and WKT is manipulated with GeoTools. The current version of the library works with Oracle geospatial databases and relies on Jena.