# Attaching metadata to data resources and distributions with DCAT

## Considerations

The need to attach metadata to data description is very general (not only for statistics)

There are different types of metadata: structural, descriptive, quality, provenance, etc.

Currently, it is possible to attach elements of SDMX structural metadata and quality indicators using DQV to DCAT descriptions using the StatDCAT application profile, but:

- this is limited to SDMX
- StatDCAT-AP relies on an old version of DCAT
- The StatDCAT-AP governance is unclear

## Proposal

The idea is to propose an OWL object property named `metadata` (or `hasMetadata`, or something like that, depending on naming policies) which would be used to attach "bundles" of metadata resources to DCAT constructs.

Referring to the [DCAT v3](https://www.w3.org/TR/vocab-dcat-3/) model, we should be able to attach metadata to pretty much any DCAT construct, so the domain of the property should be the union of `dcat:Resource` and `dcat:Distribution`.

Regarding the range, one can think of creating a `MetadataBundle` which would be an aggregation of metadata resources (with aggregation mechanisms like OAI-ORE, FDO or PROV-O, for example), but the object resource could be anything, so the best would probably be to leave the range open.

So the definition of the property would be something like (showing only English texts):

dcat:metadata
  a owl:ObjectProperty ;
  rdfs:label "metadata"@en ;
  rdfs:comment "A collection of metadata resources that describe the structure, contents, quality, provenance, etc., of the resource or distribution"@en ;
  skos:definition "A collection of metadata resources that describe the structure, contents, quality, provenance, etc., of the resource or distribution"@en ;
  rdfs:domain [
      a owl:Class ;
      owl:unionOf (
          dcat:Resource
          dcat:Distribution
        ) ;
  skos:scopeNote "The range of this property is intentionally left open, with the purpose of allowing the attachment of different types of metadata."@en .

## Alternatives

If it proves unfeasible to add the `metadata` property to DCAT in a future version, other possibilities are:

- add the property to the DCAT-AP profile or create a specific profile
- create an inverse `metadataFor` property in another standard vocabulary, for example DDI-CDI (*NB*: [COOS](https://github.com/linked-statistics/COOS) defines a [`metadataFor`](https://github.com/linked-statistics/COOS/blob/master/coos.ttl#L346) property that could be adapted)