cheat sheets.

Namespaces:
  rdfs: http://www.w3.org/2000/01/rdf-schema#
  rdf:  http://www.w3.org/1999/02/22-rdf-syntax-ns#
  owl:  http://www.w3.org/2002/07/owl#
  xsd:  http://www.w3.org/2001/XMLSchema#
  skos: http://www.w3.org/2004/02/skos/core#