How a dataset’s files wrote one field of one class
(CimDataset::field_forms). Each part is the first the files showed;
a field written two ways keeps the first.
Whether text looks like CGMES or NC RDF/XML: near the top it names one
of the two CIM namespaces, an NC profile (https://ap.cim4.eu/, which a
header’s dcterms:conformsTo names: an NC dataset may be its DCAT header
alone) or ENTSO-E reference data (https://energy.referencedata.eu/,
SKOS/DCAT with no CIM namespace).