bu-core3d:BuildingGeometry3DLoD.verticalGeometryReference3DBottom
http://inspire.ec.europa.eu/ont/bu-core3d#BuildingGeometry3DLoD.verticalGeometryReference3DBottom
rdfs:comment
http://www.w3.org/2000/01/rdf-schema#comment
EXAMPLE: generalGround, bottomOfConstruction.
@en
graph:default
https://triplydb.com/inspire/bu-core3d/graphs/default