1. Advanced tourism planning system (ATLAS).
http://atlas.web.auth.gr/
2. Dublin Core Metadata Initiative (DCMI) Metadata Terms.
http://dublincore.org/documents/dcmi-terms/
3. FOAF Vocabulary Specification.
http://xmlns.com/foaf/spec/20140114.html
4. GeoNames Ontology.
http://www.geonames.org/ontology/
5. Neo4j, the World’s Leading Graph Database.
http://neo4j.com/