Reference system mapped to `dct:conformsTo`

[jakubklimek]

Problem statement In GeoDCAT-AP 2.0.0, the Reference system property on

• Catalogue
• Data Service
• Dataset and
• Distribution

is mapped to the generic dct:conformsTo, which is also present on the same classes, both having dct:Standard as range.

This makes correct assignment of usage notes, labels and the required code lists rather difficult, as well as consequent validation e.g. via SHACL. The current approach is not in line with the profiling guidelines established in the context of the SEMIC Style Guide property reuse guideline Reuse of a property with terminological adaptations and Reuse of a property with semantic adaptations. Also, the approach becomes even more problematic in a cross-profile environment where incompatible requirements can be easily made.

The reference system usage note says e.g. This property SHOULD be used to specify the reference system used in the Catalogue. Spatial reference systems SHOULD be specified by using the corresponding URIs from the “EPSG coordinate reference systems” register operated by OGC [OGC-EPSG].

The dct:conformsTo usage note says e.g. This property refers to an implementing rule or other specification.

Proposal Either

1. Merge the usage notes to the generic dct:conformsTo to make it clear that reference systems are one kind of the Standards expected as values here, or
2. Introduce a profile specific subproperty of dct:conformsTo geodcatap:referenceSystem and attach the separate usage notes there.