osmmeta:key
https://wiki.openstreetmap.org/meta/key
rdfs:comment
http://www.w3.org/2000/01/rdf-schema#comment
A key is used to link an OSM data item to the underlying OSM metadata.
graph:custom-model
https://iamlabdemo.triply.cc/openstreetmap/openstreetmap/graphs/custom-model