% Join graph metadata in the default graph with data from the named graph.
rdf(S, iri("https://example.org/reportedBy"), Station, default_graph) :-
  rdf(
    iri("https://example.org/sensorGraph"),
    iri("https://example.org/reportedBy"),
    Station,
    default_graph
  ),
  rdf(
    S,
    iri("https://example.org/temperature"),
    _,
    iri("https://example.org/sensorGraph")
  ).