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ckanext-dcat

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Ckanext-dcat is a CKAN extension that helps data publishers expose and consume metadata as serialized RDF documents using DCAT, as well as others metadata formats like Croissant ML or Schema.org.

{
    "id": "425e361b-bad9-4a8f-8cc4-2e147c4e8c18",
    "name": "my-ckan-dataset",
    "title": "An example CKAN dataset",
    "description": "Some notes about the data",
    "temporal_coverage": [
        {
            "start": "2024-01-01",
            "end": "2024-12-31"
        }
    ],
    "resources": [
        {
            "id": "df0fc449-fddf-41af-910a-f972b458956c",
            "name": "Some data in CSV format",
            "url": "http://my-ckan-site.org/dataset/425e361b-bad9-4a8f-8cc4-2e147c4e8c18/resource/df0fc449-fddf-41af-910a-f972b458956c/download/data.csv",
            "format": "CSV"
        }
    ]
}

@prefix dcat: <http://www.w3.org/ns/dcat#> .
@prefix dct: <http://purl.org/dc/terms/> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .

<http://my-ckan-site.org/dataset/425e361b-bad9-4a8f-8cc4-2e147c4e8c18> a dcat:Dataset ;
    dct:identifier "425e361b-bad9-4a8f-8cc4-2e147c4e8c18" ;
    dct:temporal [ a dct:PeriodOfTime ;
            dcat:endDate "2024-12-31"^^xsd:date ;
            dcat:startDate "2024-01-01"^^xsd:date ] ;
    dct:title "An example CKAN dataset" ;
    dcat:distribution <http://my-ckan-site.org/dataset/425e361b-bad9-4a8f-8cc4-2e147c4e8c18/resource/df0fc449-fddf-41af-910a-f972b458956c> .

<http://my-ckan-site.org/dataset/425e361b-bad9-4a8f-8cc4-2e147c4e8c18/resource/df0fc449-fddf-41af-910a-f972b458956c> a dcat:Distribution ;
    dct:format "CSV" ;
    dct:title "Some data in CSV format" ;
    dcat:accessURL <http://my-ckan-site.org/dataset/425e361b-bad9-4a8f-8cc4-2e147c4e8c18/resource/df0fc449-fddf-41af-910a-f972b458956c/download/data.csv> .

{
  "@context": {
    "dcat": "http://www.w3.org/ns/dcat#",
    "dct": "http://purl.org/dc/terms/",
    "xsd": "http://www.w3.org/2001/XMLSchema#"
  },
  "@graph": [
    {
      "@id": "http://my-ckan-site.org/dataset/425e361b-bad9-4a8f-8cc4-2e147c4e8c18",
      "@type": "dcat:Dataset",
      "dcat:distribution": {
        "@id": "http://my-ckan-site.org/dataset/425e361b-bad9-4a8f-8cc4-2e147c4e8c18/resource/df0fc449-fddf-41af-910a-f972b458956c"
      },
      "dct:identifier": "425e361b-bad9-4a8f-8cc4-2e147c4e8c18",
      "dct:temporal": {
        "@id": "_:N1c32ba52ad1641d086101a4a4bcbe8a5"
      },
      "dct:title": "An example CKAN dataset"
    },
    {
      "@id": "_:N1c32ba52ad1641d086101a4a4bcbe8a5",
      "@type": "dct:PeriodOfTime",
      "dcat:endDate": {
        "@type": "xsd:date",
        "@value": "2024-12-31"
      },
      "dcat:startDate": {
        "@type": "xsd:date",
        "@value": "2024-01-01"
      }
    },
    {
      "@id": "http://my-ckan-site.org/dataset/425e361b-bad9-4a8f-8cc4-2e147c4e8c18/resource/df0fc449-fddf-41af-910a-f972b458956c",
      "@type": "dcat:Distribution",
      "dcat:accessURL": {
        "@id": "http://my-ckan-site.org/dataset/425e361b-bad9-4a8f-8cc4-2e147c4e8c18/resource/df0fc449-fddf-41af-910a-f972b458956c/download/data.csv"
      },
      "dct:format": "CSV",
      "dct:title": "Some data in CSV format"
    }
  ]
}

In terms of CKAN features, this extension offers:

  • Pre-built CKAN schemas for common Application Profiles that can be adapted to each site requirements to provide out-of-the-box DCAT support in data portals, including tailored form fields, validation etc. (currently supporting DCAT-AP v1.1, v2.1 and v3 and DCAT-US v3).

  • DCAT Endpoints that expose the catalog datasets in different RDF serializations (dcat plugin).

  • An RDF Harvester that allows importing RDF serializations from other catalogs to create CKAN datasets (dcat_rdf_harvester plugin).

  • Other features like Command Line Interface, support for indexing in Google Dataset Search or endpoints for exposing dataets in the Croissant ML format.

These are implemented internally using:

  • A base mapping between DCAT and CKAN datasets and viceversa (compatible with DCAT-AP v1.1, v2.1 and v3 and DCAT-US v3).

  • An RDF Parser that allows to read RDF serializations in different formats and extract CKAN dataset dicts, using customizable profiles.

  • An RDF Serializer that allows to transform CKAN datasets metadata to different semantic formats, also allowing customizable profiles.