DCAT ↔ CKAN mapping

RDF DCAT to CKAN dataset mapping¶

The following table provides a generic mapping between the fields of the dcat:Dataset and dcat:Distribution classes and their equivalents in the CKAN model. In most cases this mapping is deliberately a loose one. For instance, it does not try to link the DCAT publisher property with a CKAN dataset author, maintainer or organization, as the link between them is not straight-forward and may depend on a particular instance needs. When mapping from CKAN metadata to DCAT though, there are in some cases fallback fields that are used if the default field is not present (see RDF Serializer for more details on this).

This mapping is compatible with DCAT-AP v1.1, v2.1 and v3 and DCAT-US v3. It depends on the active profile(s) and the fields present in your custom schema which DCAT properties are mapped.

Sites are encouraged to use ckanext-scheming to manage their metadata schema (see Schemas for all details). This changes in some cases the way metadata is stored internally and presented at the CKAN API level, but should not affect the RDF DCAT output.

Note

Fields prefixed with custom: are custom metadata fields defined via ckanext-scheming. When using euro_dcat_ap and euro_dcat_ap_2 based profiles, these could also be actual extra fields (e.g. extras=[{"key": "issued", "value": "2024"}]). It is recommended that site maintainers start to migrate to custom fields by using the euro_dcat_ap_scheming profile as this fields are properly validated, can use the scheming snippets etc. See Schemas for more details.

DCAT class	DCAT property	CKAN dataset field	CKAN fallback fields	Stored as
dcat:Dataset	-	custom:uri		text	See URIs
dcat:Dataset	dct:title	title		text
dcat:Dataset	dct:description	notes		text
dcat:Dataset	dcat:keyword	tags		text
dcat:Dataset	dcat:theme	custom:theme		list	See Lists
dcat:Dataset	dct:identifier	custom:identifier	custom:guid, id	text
dcat:Dataset	adms:identifier	custom:alternate_identifier		text
dcat:Dataset	dct:issued	custom:issued	metadata_created	text
dcat:Dataset	dct:modified	custom:modified	metadata_modified	text
dcat:Dataset	owl:versionInfo	version	custom:dcat_version	text
dcat:Dataset	adms:versionNotes	custom:version_notes		text
dcat:Dataset	dct:language	custom:language		list	See Lists
dcat:Dataset	dcat:landingPage	url		text
dcat:Dataset	dct:accrualPeriodicity	custom:frequency		text
dcat:Dataset	dct:conformsTo	custom:conforms_to		list	See Lists
dcat:Dataset	dct:accessRights	custom:access_rights		text
dcat:Dataset	foaf:page	custom:documentation		list	See Lists
dcat:Dataset	dct:provenance	custom:provenance		text
dcat:Dataset	dcat-us:liabilityStatement	custom:liability		text	DCAT-US v3 and higher only
dcat:Dataset	dcat-us:purpose	custom:purpose		text	DCAT-US v3 and higher only
dcat:Dataset	skos:scopeNote	custom:usage		text	DCAT-US v3 and higher only
dcat:Dataset	dct:type	custom:dcat_type		text
dcat:Dataset	prov:wasGeneratedBy	custom:provenance_activity		text
dcat:Dataset	prov:qualifiedAttribution	custom:qualified_attribution		list	See Lists. Object should contain agent and role
dcat:Dataset	dcat:hasVersion	custom:has_version		list	See Lists. It is assumed that these are one or more URIs referring to another dcat:Dataset
dcat:Dataset	dct:isVersionOf	custom:is_version_of		list	See Lists. It is assumed that these are one or more URIs referring to another dcat:Dataset
dcat:Dataset	dct:source	custom:source		list	See Lists. It is assumed that these are one or more URIs referring to another dcat:Dataset
dcat:Dataset	adms:sample	custom:sample		list	See Lists. It is assumed that these are one or more URIs referring to dcat:Distribution instances
dcat:Dataset	dct:spatial	custom:spatial_uri		text	See Spatial coverage
dcat:Dataset	dct:temporal	custom:temporal_start + custom:temporal_end		text	None, one or both extras can be present
dcat:Dataset	dcat-us:geographicBoundingBox	custom:bbox		list of objects	DCAT-US v3 and higher only
dcat:Dataset	dcat-us:describedBy	custom:data_dictionary		list of objects	DCAT-US v3 and higher only
dcat:Dataset	dcat:temporalResolution	custom:temporal_resolution		list
dcat:Dataset	dcat:spatialResolutionInMeters	custom:spatial_resolution_in_meters		list
dcat:Dataset	dct:isReferencedBy	custom:is_referenced_by		list
dcat:Dataset	dct:publisher	custom:publisher_uri		list of objects	See URIs and Publisher
foaf:Agent	foaf:name	custom:publisher_name		text
foaf:Agent	foaf:mbox	custom:publisher_email	organization:title	text
foaf:Agent	foaf:homepage	custom:publisher_url		text
foaf:Agent	dct:type	custom:publisher_type		text
foaf:Agent	dct:identifier	custom:publisher_id		text
dcat:Dataset	dct:creator	custom:creator_uri		list of objects	See URIs
foaf:Agent	foaf:name	custom:creator_name		text
foaf:Agent	foaf:mbox	custom:creator_email	organization:title	text
foaf:Agent	foaf:homepage	custom:creator_url		text
foaf:Agent	dct:type	custom:creator_type		text
foaf:Agent	dct:identifier	custom:creator_id		text
dcat:Dataset	dct:contributor	custom:contributor		list of objects	See URIs. The object properties are the same than publishers and creators. DCAT-US v3 and higher only
dcat:Dataset	dcat:contactPoint	custom:contact_uri		list of objects	See URIs and Contact points
vcard:Kind	vcard:fn	custom:contact_name	maintainer, author	text
vcard:Kind	vcard:hasEmail	custom:contact_email	maintainer_email, author_email	text
vcard:Kind	vcard:hasUID	custom:contact_identifier		text
dcat:Dataset	dcat:distribution	resources		text
dcat:Distribution	-	resource:uri		text	See URIs
dcat:Distribution	dct:title	resource:name		text
dcat:Distribution	dcat:accessURL	resource:access_url	resource:url	text	If downloadURL is not present, accessURL will be used as resource url
dcat:Distribution	dcat:downloadURL	resource:download_url		text	If present, downloadURL will be used as resource url
dcat:Distribution	dct:description	resource:description		text
dcat:Distribution	dcat:mediaType	resource:mimetype		text
dcat:Distribution	dct:format	resource:format		text
dcat:Distribution	dct:license	resource:license		text	See Licenses
dcat:Distribution	adms:status	resource:status		text
dcat:Distribution	dcat:byteSize	resource:size		number
dcat:Distribution	dct:issued	resource:issued	created	text
dcat:Distribution	dct:modified	resource:modified	metadata_modified	text
dcat:Distribution	dct:rights	resource:rights		text
dcat:Distribution	foaf:page	resource:documentation		list	See Lists
dcat:Distribution	dct:language	resource:language		list	See Lists
dcat:Distribution	dct:conformsTo	resource:conforms_to		list	See Lists
dcat:Distribution	dcatap:availability	resource:availability		text
dcat:Distribution	dcat:compressFormat	resource:compress_format		text
dcat:Distribution	dcat:packageFormat	resource:package_format		text
dcat:Distribution	cnt:characterEncoding	resource:package_format		text	DCAT-US v3 and higher only
dcat:Distribution	dct:identifier	custom:identifier	custom:guid, id	text	DCAT-US v3 and higher only
dcat:Distribution	dcat-us:describedBy	custom:data_dictionary		list of objects	DCAT-US v3 and higher only
dcat:Distribution	dcat:accessService	resource:access_services		list of objects

Custom fields¶

Fields marked as custom: are stored as free form extras in the euro_dcat_ap and euro_dcat_ap_2 profiles, but stored as first level custom fields when using the scheming based profile (euro_dcat_ap_scheming), i.e:

{
    "name": "test_dataset_dcat",
    "extras": [
         {"key": "version_notes", "value": "Some version notes"}
    ]
}

vs:

{
    "name": "test_dataset_dcat",
    "version_notes": "Some version notes"
}

URIs¶

Whenever possible, URIs are extracted and stored so there is a clear reference to the original RDF resource. For instance:

<?xml version="1.0" encoding="utf-8" ?>
<rdf:RDF
 xmlns:dct="http://purl.org/dc/terms/"
 xmlns:dcat="http://www.w3.org/ns/dcat#"
 xmlns:foaf="http://xmlns.com/foaf/0.1/"
 xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">

<dcat:Dataset rdf:about="http://data.some.org/catalog/datasets/1">
  <dct:title>Dataset 1</dct:title>
  <dct:publisher>
    <foaf:Organization rdf:about="http://orgs.vocab.org/some-org">
      <foaf:name>Publishing Organization for dataset 1</foaf:name>
    </foaf:Organization>
  </dct:publisher>
<!-- ... -->
</dcat:Dataset>
</rdf:RDF>

{
    "title": "Dataset 1",
    "extras": [
        {"key": "uri", "value": "http://data.some.org/catalog/datasets/1"},
        {"key": "publisher_uri", "value": "http://orgs.vocab.org/some-org"},
        {"key": "publisher_name", "value": "Publishing Organization for dataset 1"}
    ]
}

Another example:

@prefix dcat:    <http://www.w3.org/ns/dcat#> .
@prefix dct:     <http://purl.org/dc/terms/> .
@prefix rdf:     <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .

<http://data.some.org/catalog/datasets/1>
      a       dcat:Dataset ;
      dct:title "Dataset 1" ;
      dcat:distribution
              <http://data.some.org/catalog/datasets/1/d/1> .


<http://data.some.org/catalog/datasets/1/d/1>
      a       dcat:Distribution ;
      dct:title "Distribution for dataset 1" ;
      dcat:accessURL <http://data.some.org/catalog/datasets/1/downloads/1.csv> .

{
    "title": "Dataset 1",
    "extras": [
        {"key": "uri", "value": "http://data.some.org/catalog/datasets/1"}
    ],
    "resources": [{
        "name": "Distribution for dataset 1",
        "url": "http://data.some.org/catalog/datasets/1/downloads/1.csv",
        "uri": "http://data.some.org/catalog/datasets/1/d/1"
    }]
}

Lists¶

On the legacy profiles, lists are stored as a JSON string, eg:

@prefix dcat:  <http://www.w3.org/ns/dcat#> .
@prefix dct:   <http://purl.org/dc/terms/> .
@prefix rdf:   <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .

<http://example.com/data/test-dataset-1>
    a                  dcat:Dataset ;
    dct:title       "Dataset 1" ;
    dct:language    "ca" , "en" , "es" ;
    dcat:theme      "http://eurovoc.europa.eu/100142" , "http://eurovoc.europa.eu/209065", "Earth Sciences" ;

{
    "title": "Dataset 1",
    "extras": [
        {"key": "uri", "value": "http://data.some.org/catalog/datasets/1"},
        {"key": "language", "value": "[\"ca\", \"en\", \"es\"]"},
        {"key": "theme", "value": "[\"Earth Sciences\", \"http://eurovoc.europa.eu/209065\", \"http://eurovoc.europa.eu/100142\"]"}
    ]
}

On the scheming-based ones, these are shown as actual lists:

{
    "title": "Dataset 1",
    "uri": "http://data.some.org/catalog/datasets/1"},
    "language": ["ca", "en", "es"],
    "theme": ["Earth Sciences", "http://eurovoc.europa.eu/209065", "http://eurovoc.europa.eu/100142"]
}

Contact points and Publisher¶

Properties for dcat:contactPoint and dct:publisher are stored as namespaced extras in the legacy profiles. When using a scheming-based profile, these are stored as proper objects (and multiple instances are allowed for contact point):

{
    "name": "test_dataset_dcat",
    "title": "Test dataset DCAT",
    "extras": [
        {"key":"contact_name","value":"PointofContact"},
        {"key":"contact_email","value":"contact@some.org"}
    ],
}

vs:

{
    "name": "test_dataset_dcat",
    "title": "Test dataset DCAT",
    "contact": [
        {
            "name": "Point of Contact 1",
            "email": "contact1@some.org"
        },
        {
            "name": "Point of Contact 2",
            "email": "contact2@some.org"
        },
    ]
}

If no publisher or publisher_* fields are found, the serializers will fall back to getting the publisher properties from the organization the CKAN dataset belongs to. The organization schema can be customized with the schema located in ckanext/dcat/schemas/publisher_organization.yaml to provide the extra properties supported (this will additionally require loading the scheming_organizations plugin in ckan.plugins).

Spatial coverage¶

The following formats for dct:spatial are supported by the default parser. Note that the default serializer will return the single dct:spatial instance form by default.

One dct:spatial instance, URI only

<dct:spatial rdf:resource="http://geonames/Newark"/>

One dct:spatial instance with text (this should not be used anyway)
```
<dct:spatial>Newark</dct:spatial>
```

One dct:spatial instance with label and/or geometry

<dct:spatial rdf:resource="http://geonames/Newark">
    <dct:Location>
        <locn:geometry rdf:datatype="https://www.iana.org/assignments/media-types/application/vnd.geo+json">
            {"type": "Polygon", "coordinates": [[[175.0, 17.5], [-65.5, 17.5], [-65.5, 72.0], [175.0, 72.0], [175.0, 17.5]]]}
        </locn:geometry>
        <locn:geometry rdf:datatype="http://www.opengis.net/ont/geosparql#wktLiteral">
            POLYGON ((175.0000 17.5000, -65.5000 17.5000, -65.5000 72.0000, 175.0000 72.0000, 175.0000 17.5000))
        </locn:geometry>
        <skos:prefLabel>Newark</skos:prefLabel>
    </dct:Location>
</dct:spatial>

Multiple dct:spatial instances (as in GeoDCAT-AP)

<dct:spatial rdf:resource="http://geonames/Newark"/>
<dct:spatial>
    <dct:Location>
        <locn:geometry rdf:datatype="https://www.iana.org/assignments/media-types/application/vnd.geo+json">
            {"type": "Polygon", "coordinates": [[[175.0, 17.5], [-65.5, 17.5], [-65.5, 72.0], [175.0, 72.0], [175.0, 17.5]]]}
        </locn:geometry>
        <locn:geometry rdf:datatype="http://www.opengis.net/ont/geosparql#wktLiteral">
            POLYGON ((175.0000 17.5000, -65.5000 17.5000, -65.5000 72.0000, 175.0000 72.0000, 175.0000 17.5000))
        </locn:geometry>
    </dct:Location>
</dct:spatial>
<dct:spatial>
    <dct:Location rdf:nodeID="N8c2a57d92e2d48fca3883053f992f0cf">
        <skos:prefLabel>Newark</skos:prefLabel>
    </dct:Location>
</dct:spatial>

If the RDF provides them, profiles should store the textual and geometric representation of the location in:

For legacy profiles in spatial_text, spatial_bbox, spatial_centroid or spatial (for any other geometries) extra fields
For scheming-based profiles in objects in the spatial_coverage field, for instance:

{
    "name": "test_dataset_dcat",
    "title": "Test dataset DCAT",
    "spatial_coverage": [
        {
            "geom": {
                "type": "Polygon",
                "coordinates": [...]
            },
            "text": "Tarragona",
            "uri": "https://sws.geonames.org/6361390/",
            "bbox": {
                "type": "Polygon",
                "coordinates": [
                    [
                        [-2.1604, 42.7611],
                        [-2.0938, 42.7611],
                        [-2.0938, 42.7931],
                        [-2.1604, 42.7931],
                        [-2.1604, 42.7611],
                    ]
                ],
            },
            "centroid": {"type": "Point", "coordinates": [1.26639, 41.12386]},
        }
    ]
}

Licenses¶

In the CKAN model, the license field is stored at the dataset level whereas in the DCAT model it is stored at Distributions level. By default, the RDF parser will try to find a distribution with a license that matches one of those registered in CKAN and attach this license to the dataset. The first matching distribution's license is used, meaning that any discrepancy accross distributions license will not be accounted for. This behavior can be customized by overridding the _license() method on a custom profile.

When serializing, distributions can inherit the license from the dataset if ckanext.dcat.resource.inherit.license is set to true.