DCAT is an RDF vocabulary designed to facilitate interoperability between data catalogs published on the Web. This document defines the schema and provides examples for its use.

By using DCAT to describe datasets in data catalogs, publishers increase discoverability and enable applications easily to consume metadata from multiple catalogs. It further enables decentralized publishing of catalogs and facilitates federated dataset search across sites. Aggregated DCAT metadata can serve as a manifest file to facilitate digital preservation.

The original DCAT vocabulary was developed at DERI, refined by the eGov Interest Group, and then finally standardized by the Government Linked Data (GLD) Working Group.

DCAT incorporates terms from pre-existing vocabularies, where stable terms with appropriate meanings could be found, such as foaf:homepage and dct:title. Informal summary definitions of these terms are included here for convenience, while complete definitions are available in the provided authoritative references. Changes to definitions in those references, if any, will supersede the summaries given in this specification. Note that conformance to DCAT (Section 3) concerns usage of only the terms in the DCAT namespace itself, so possible changes to the external definitions will not affect conformance of DCAT implementations.

Introduction

Data can come in many formats, ranging from spreadsheets over XML and RDF to various speciality formats. DCAT does not make any assumptions about the format of the datasets described in a catalog. Other, complementary vocabularies may be used together with DCAT to provide more detailed format-specific information. For example, properties from the VoID vocabulary [[void]] can be used to express various statistics about a DCAT-described dataset if that dataset is in RDF format.

This document does not prescribe any particular method of deploying data expressed in DCAT. DCAT is applicable in many contexts including RDF accessible via SPARQL endpoints, embedded in HTML pages as RDFa, or serialized as e.g. RDF/XML or Turtle. The examples in this document use Turtle simply because of Turtle's readability.

Namespaces

The namespace for DCAT is http://www.w3.org/ns/dcat#. However, it should be noted that DCAT makes extensive use of terms from other vocabularies, in particular Dublin Core. DCAT itself defines a minimal set of classes and properties of its own. A full set of namespaces and prefixes used in this document is shown in the table below.

PrefixNamespace
dcathttp://www.w3.org/ns/dcat#
dcthttp://purl.org/dc/terms/
dctypehttp://purl.org/dc/dcmitype/
foafhttp://xmlns.com/foaf/0.1/
rdfhttp://www.w3.org/1999/02/22-rdf-syntax-ns#
rdfshttp://www.w3.org/2000/01/rdf-schema#
skoshttp://www.w3.org/2004/02/skos/core#
vcardhttp://www.w3.org/2006/vcard/ns#
xsdhttp://www.w3.org/2001/XMLSchema#
A data catalog conforms to DCAT if: A DCAT profile is a specification for data catalogs that adds additional constraints to DCAT. A data catalog that conforms to the profile also conforms to DCAT. Additional constraints in a profile MAY include:

Vocabulary Overview

DCAT is an RDF vocabulary well-suited to representing government data catalogs such as Data.gov and data.gov.uk. DCAT defines three main classes:

Notice that a dataset in DCAT is defined as a "collection of data, published or curated by a single agent, and available for access or download in one or more formats". A dataset does not have to be available as a downloadable file. For example, a dataset that is available via an API can be defined as an instance of dcat:Dataset and the API can be defined as an instance of dcat:Distribution. DCAT itself does not define properties specific to APIs description. These are considered out of the scope of this version of the vocabulary. Nevertheless, this can be defined as a profile of the DCAT vocabulary.

Another important class in DCAT is dcat:CatalogRecord which describes a dataset entry in the catalog. Notice that while dcat:Dataset represents the dataset itself, dcat:CatalogRecord represents the record that describes a dataset in the catalog. The use of the CatalogRecord is considered optional. It is used to capture provenance information about dataset entries in a catalog. If this distinction is not necessary then CatalogRecord can be safely ignored.

UML model of DCAT classes and properties

All RDF examples in this document are written in Turtle syntax [[turtle]].

Basic Example

This example provides a quick overview of how DCAT might be used to represent a government catalog and its datasets.

First, the catalog description:

   :catalog
       a dcat:Catalog ;
       dct:title "Imaginary Catalog" ;
       rdfs:label "Imaginary Catalog" ;
       foaf:homepage <http://example.org/catalog> ;
       dct:publisher :transparency-office ;
       dct:language <http://id.loc.gov/vocabulary/iso639-1/en>  ;
       dcat:dataset :dataset-001  , :dataset-002 , :dataset-003 ; 
       .

The publisher of the catalog has the relative URI :transparency-office. Further description of the publisher can be provided as in the following example:

   :transparency-office
       a foaf:Organization ;
       rdfs:label "Transparency Office" ;
       .

The catalog lists each of its datasets via dcat:dataset property. In the example above, an example dataset was mentioned with the relative URI :dataset-001. A possible description of it using DCAT is shown below:

   :dataset-001
       a dcat:Dataset ;
       dct:title "Imaginary dataset" ;
       dcat:keyword "accountability","transparency" ,"payments" ;
       dct:issued "2011-12-05"^^xsd:date ;
       dct:modified "2011-12-05"^^xsd:date ;
       dcat:contactPoint <http://example.org/transparency-office/contact> ;
       dct:temporal <http://reference.data.gov.uk/id/quarter/2006-Q1> ;
       dct:spatial <http://www.geonames.org/6695072> ;
       dct:publisher :finance-ministry ;
       dct:language <http://id.loc.gov/vocabulary/iso639-1/en>  ;
       dct:accrualPeriodicity <http://purl.org/linked-data/sdmx/2009/code#freq-W>  ;
       dcat:distribution :dataset-001-csv ;
       .

In order to express frequency of update in the example above, we chose to use an instance from the Content-Oriented Guidelines developed as part of the W3C Data Cube Vocabulary efforts. Additionally, we chose to describe the spatial and temporal coverage of the example dataset using URIs from Geonames and the Interval dataset from data.gov.uk, respectively. A contact point is also provided where comments and feedback about the dataset can be sent. Further details about the contact point, such as email address or telephone number, can be provided using VCard [[vcard-rdf]].

The dataset distribution :dataset-001-csv can be downloaded as a 5Kb CSV file. This information is represented via an RDF resource of type dcat:Distribution.

   :dataset-001-csv
       a dcat:Distribution ;
       dcat:downloadURL <http://www.example.org/files/001.csv> ;
       dct:title "CSV distribution of imaginary dataset 001" ;
       dcat:mediaType "text/csv" ;
       dcat:byteSize "5120"^^xsd:decimal ;
       .

Classifying datasets

The catalog classifies its datasets according to a set of domains represented by the relative URI :themes. SKOS can be used to describe the domains used:

   :catalog dcat:themeTaxonomy :themes .
   :themes
       a skos:ConceptScheme ;
       skos:prefLabel "A set of domains to classify documents" ;
       .
   :dataset-001 dcat:theme :accountability  .

Notice that this dataset is classified under the domain represented by the relative URI :accountability. It is recommended to define the concept as part of the concepts scheme identified by the URI :themes that was used to describe the catalog domains. An example SKOS description:

   :accountability 
       a skos:Concept ;
       skos:inScheme :themes ;
       skos:prefLabel "Accountability" ;
       .

Describing catalog records metadata

If the catalog publisher decides to keep metadata describing its records (i.e. the records containing metadata describing the datasets), dcat:CatalogRecord can be used. For example, while  :dataset-001 was issued on 2011-12-05, its description on Imaginary Catalog was added on 2011-12-11. This can be represented by DCAT as in the following:

   :catalog  dcat:record :record-001  .
   :record-001
       a dcat:CatalogRecord ;
       foaf:primaryTopic :dataset-001 ;
       dct:issued "2011-12-11"^^xsd:date ;
       .  

A dataset available only behind some Web page

:dataset-002 is available as a CSV file. However :dataset-002 can only be obtained through some Web page where the user needs to click some links, provide some information and check some boxes before accessing the data

   :dataset-002 
       a dcat:Dataset ;
       dcat:landingPage <http://example.org/dataset-002.html> ;
       dcat:distribution :dataset-002-csv ;
       .
   :dataset-002-csv 
       a dcat:Distribution ;
       dcat:accessURL <http://example.org/dataset-002.html> ;
       dcat:mediaType "text/csv" ;
       .
Notice the use of dcat:landingPage and the definition of the dcat:Distribution instance.

A dataset available as download and behind some Web page

On the other hand, :dataset-003 can be obtained through some landing page but also can be downloaded from a known URL.

   :dataset-003 
       a dcat:Dataset ;
       dcat:landingPage <http://example.org/dataset-003.html> ;
       dcat:distribution :dataset-003-csv ;
       .
   :dataset-003-csv 
       a dcat:Distribution ;
       dcat:downloadURL <http://example.org/dataset-003.csv> .
       dcat:mediaType "text/csv" ;
       .
Notice that we used dcat:downloadURL with the downloadable distribution and that the other distribution through the landing page does not have to be defined as a separate dcat:Distribution instance.

Vocabulary specification

The definitions (including domain and range) of terms outside the dcat namespace are provided here only for convenience and must not be considered normative. The authoritative definitions of these terms are in the corresponding specifications: [[!DC11]], [[!FOAF]], [[!RDF-SCHEMA]], [[!SKOS-REFERENCE]], [[!xmlschema-2]] and [[!vcard-rdf]].

Class: Catalog

The following properties are recommended for use on this class: catalog record, dataset, description, homepage, language, license, publisher, release date, rights, spatial, themes, title, update date

RDF Class:dcat:Catalog
Definition:A data catalog is a curated collection of metadata about datasets.
Usage note:Typically, a web-based data catalog is represented as a single instance of this class.
See also: Catalog record, Dataset

Property: title

RDF Property:dct:title
Definition:A name given to the catalog.
Range:rdfs:Literal

Property: description

RDF Property:dct:description
Definition:A free-text account of the catalog.
Range:rdfs:Literal

Property: release date

RDF Property:dct:issued
Definition:Date of formal issuance (e.g., publication) of the catalog.
Range:rdfs:Literal encoded using the relevant ISO 8601 Date and Time compliant string and typed using the appropriate XML Schema datatype [[xmlschema-2]]
See also: dataset release date, catalog record listing date and distribution release date

Property: update/modification date

RDF Property:dct:modified
Definition:Most recent date on which the catalog was changed, updated or modified.
Range:rdfs:Literal encoded using the relevant ISO 8601 Date and Time compliant string and typed using the appropriate XML Schema datatype [[xmlschema-2]]
See also: dataset modification date, catalog record modification date and distribution modification date

Property: language

RDF Property:dct:language
Definition:The language of the catalog. This refers to the language used in the textual metadata describing titles, descriptions, etc. of the datasets in the catalog.
Range: dct:LinguisticSystem
Resources defined by the Library of Congress (1, 2) SHOULD be used.
If a ISO 639-1 (two-letter) code is defined for language, then its corresponding IRI SHOULD be used; if no ISO 639-1 code is defined, then IRI corresponding to the ISO 639-2 (three-letter) code SHOULD be used.
Usage note:Multiple values can be used. The publisher might also choose to describe the language on the dataset level (see dataset language).

Property: homepage

RDF Property:foaf:homepage
Definition:The homepage of the catalog.
Range:foaf:Document
Usage note:foaf:homepage is an inverse functional property (IFP) which means that it should be unique and precisely identify the catalog. This allows smushing various descriptions of the catalog when different URIs are used.

Property: publisher

RDF Property:dct:publisher
Definition:The entity responsible for making the catalog online.
Usage note:Resources of type foaf:Agent are recommended as values for this property.
See also:Class: Organization/Person

Property: spatial/geographic

RDF Property:dct:spatial
Definition:The geographical area covered by the catalog.
Range:dct:Location

Property: themes

RDF Property:dcat:themeTaxonomy
Definition:The knowledge organization system (KOS) used to classify catalog's datasets.
Domain:dcat:Catalog
Range:skos:ConceptScheme

Property: license

RDF Property:dct:license
Definition:This links to the license document under which the catalog is made available and not the datasets. Even if the license of the catalog applies to all of its datasets and distributions, it should be replicated on each distribution.
Range:dct:LicenseDocument
See also:catalog rights, distribution license

Property: rights

RDF Property:dct:rights
Definition:This describes the rights under which the catalog can be used/reused and not the datasets. Even if theses rights apply to all the catalog datasets and distributions, it should be replicated on each distribution.
Range:dct:RightsStatement
See also:catalog license, distribution rights

Property: dataset

RDF Property:dcat:dataset
Definition:A dataset that is part of the catalog.
Sub property of:dct:hasPart
Domain:dcat:Catalog
Range:dcat:Dataset

Property: catalog record

RDF Property:dcat:record
Definition:A catalog record that is part of the catalog.
Domain:dcat:Catalog
Range:dcat:CatalogRecord

Class: Catalog record

The following properties are recommended for use on this class: description, listing date, primary topic, title, update date

RDF Class:dcat:CatalogRecord
Definition:A record in a data catalog, describing a single dataset.
Usage noteThis class is optional and not all catalogs will use it. It exists for catalogs where a distinction is made between metadata about a dataset and metadata about the dataset's entry in the catalog. For example, the publication date property of the dataset reflects the date when the information was originally made available by the publishing agency, while the publication date of the catalog record is the date when the dataset was added to the catalog. In cases where both dates differ, or where only the latter is known, the publication date should only be specified for the catalog record. Notice that the W3C PROV Ontology [[prov-o]] allows describing further provenance information such as the details of the process and the agent involved in a particular change to a dataset.
See alsoDataset

If a catalog is represented as an RDF Dataset with named graphs (as defined in [[sparql11-query]]), then it is appropriate to place the description of each dataset (consisting of all RDF triples that mention the dcat:Dataset, dcat:CatalogRecord, and any of its dcat:Distributions) into a separate named graph. The name of that graph should be the IRI of the catalog record.

Property: title

RDF Property:dct:title
Definition:A name given to the record.
Range:rdfs:Literal

Property: description

RDF Property:dct:description
Definition:free-text account of the record.
Range:rdfs:Literal

Property: listing date

RDF Property:dct:issued
Definition:The date of listing the corresponding dataset in the catalog.
Range:rdfs:Literal encoded using the relevant ISO 8601 Date and Time compliant string and typed using the appropriate XML Schema datatype [[xmlschema-2]]
Usage note:This indicates the date of listing the dataset in the catalog and not the publication date of the dataset itself.
See also: dataset release date

Property: update/modification date

RDF Property:dct:modified
Definition:Most recent date on which the catalog entry was changed, updated or modified.
Range:rdfs:Literal encoded using the relevant ISO 8601 Date and Time compliant string and typed using the appropriate XML Schema datatype [[xmlschema-2]]
Usage note:This indicates the date of last change of a catalog entry, i.e. the catalog metadata description of the dataset, and not the date of the dataset itself.
See also: dataset modification date

Property: primary topic

RDF Property:foaf:primaryTopic
Definition:Links the catalog record to the dcat:Dataset resource described in the record.
Usage note:foaf:primaryTopic property is functional: each catalog record can have at most one primary topic i.e. describes one dataset.

Class: Dataset

The following properties are recommended for use on this class: contact point, description, distribution, frequency, identifier, keyword, landing page, language, publisher, release date, spatial coverage, temporal coverage, theme, title, update date,

RDF Class:dcat:Dataset
Definition:A collection of data, published or curated by a single agent, and available for access or download in one or more formats.
Sub class of:dctype:Dataset
Usage note:This class represents the actual dataset as published by the dataset publisher. In cases where a distinction between the actual dataset and its entry in the catalog is necessary (because metadata such as modification date and maintainer might differ), the catalog record class can be used for the latter.
See also:Catalog record

Property: title

RDF Property:dct:title
Definition:A name given to the dataset.
Range:rdfs:Literal

Property: description

RDF Property:dct:description
Definition:free-text account of the dataset.
Range:rdfs:Literal

Property: release date

RDF Property:dct:issued
Definition:Date of formal issuance (e.g., publication) of the dataset.
Range:rdfs:Literal encoded using the relevant ISO 8601 Date and Time compliant string and typed using the appropriate XML Schema datatype [[xmlschema-2]]
Usage note:This property should be set using the first known date of issuance.

Property: update/modification date

RDF Property:dct:modified
Definition:Most recent date on which the dataset was changed, updated or modified.
Range:rdfs:Literal encoded using the relevant ISO 8601 Date and Time compliant string and typed using the appropriate XML Schema datatype [[xmlschema-2]]
Usage note:The value of this property indicates a change to the actual dataset, not a change to the catalog record. An absent value may indicate that the dataset has never changed after its initial publication, or that the date of last modification is not known, or that the dataset is continuously updated.
See also:frequency

Property: language

RDF Property:dct:language
Definition:The language of the dataset.
Range:dct:LinguisticSystem
Resources defined by the Library of Congress (1, 2) SHOULD be used.
If a ISO 639-1 (two-letter) code is defined for language, then its corresponding IRI SHOULD be used; if no ISO 639-1 code is defined, then IRI corresponding to the ISO 639-2 (three-letter) code SHOULD be used.
Usage note:
  • This overrides the value of the catalog language in case of conflict.
  • If the dataset is available in multiple languages, use multiple values for this property. If each language is available separately, define an instance of dcat:Distribution for each language and describe the specific language of each distribution using dct:language (i.e. the dataset will have multiple dct:language values and each distribution will have one of these languages as value of its dct:language property).

Property: publisher

RDF Property:dct:publisher
Definition:An entity responsible for making the dataset available.
Usage note:Resources of type foaf:Agent are recommended as values for this property.
See also:Class: Organization/Person

Property: frequency

RDF Property:dct:accrualPeriodicity
Definition:The frequency at which dataset is published.
Range:dct:Frequency (A rate at which something recurs)

Property: identifier

RDF Property:dct:identifier
Definition:A unique identifier of the dataset.
Range:rdfs:Literal
Usage note:The identifier might be used as part of the URI of the dataset, but still having it represented explicitly is useful.

Property: spatial/geographical coverage

RDF Property:dct:spatial
Definition:Spatial coverage of the dataset.
Range:dct:Location (A spatial region or named place)

Property: temporal coverage

RDF Property:dct:temporal
Definition:The temporal period that the dataset covers.
Range:dct:PeriodOfTime (An interval of time that is named or defined by its start and end dates)

Property: theme/category

RDF Property:dcat:theme
Definition:The main category of the dataset. A dataset can have multiple themes.
Sub property of:dct:subject
Domain:dcat:Dataset
Range:skos:Concept
Usage note:The set of skos:Concepts used to categorize the datasets are organized in a skos:ConceptScheme describing all the categories and their relations in the catalog.
See also:catalog themes taxonomy

Property: keyword/tag

RDF Property:dcat:keyword
Definition:A keyword or tag describing the dataset.
Domain:dcat:Dataset
Range:rdfs:Literal

Property: contact point

RDF Property:dcat:contactPoint
Definition:Link a dataset to relevant contact information which is provided using VCard [[vcard-rdf]].
Domain:dcat:Dataset
Range:vcard:Kind

Property: dataset distribution

RDF Property:dcat:distribution
Definition:Connects a dataset to its available distributions.
Domain:dcat:Dataset
Range:dcat:Distribution

Property: landing page

RDF Property:dcat:landingPage
Definition:A Web page that can be navigated to in a Web browser to gain access to the dataset, its distributions and/or additional information.
Sub property of:foaf:page
Domain:dcat:Dataset
Range:foaf:Document
Usage note: If the distribution(s) are accessible only through a landing page (i.e. direct download URLs are not known), then the landing page link SHOULD be duplicated as accessURL on a distribution. (see example 4.4)

Class: Distribution

The following properties are recommended for use on this class: access URL, byte size, description, download URL, format, license, media type, release date, rights, title, update date

RDF class:dcat:Distribution
Definition:Represents a specific available form of a dataset. Each dataset might be available in different forms, these forms might represent different formats of the dataset or different endpoints. Examples of distributions include a downloadable CSV file, an API or an RSS feed
Usage note:This represents a general availability of a dataset it implies no information about the actual access method of the data, i.e. whether it is a direct download, API, or some through Web page. The use of dcat:downloadURL property indicates directly downloadable distributions.

Property: title

RDF Property:dct:title
Definition:A name given to the distribution.
Range:rdfs:Literal

Property: description

RDF Property:dct:description
Definition:free-text account of the distribution.
Range:rdfs:Literal

Property: release date

RDF Property:dct:issued
Definition:Date of formal issuance (e.g., publication) of the distribution.
Range:rdfs:Literal encoded using the relevant ISO 8601 Date and Time compliant string and typed using the appropriate XML Schema datatype [[xmlschema-2]]
Usage note:This property should be set using the first known date of issuance.
See also: dataset release date

Property: update/modification date

RDF Property:dct:modified
Definition:Most recent date on which the distribution was changed, updated or modified.
Range:rdfs:Literal encoded using the relevant ISO 8601 Date and Time compliant string and typed using the appropriate XML Schema datatype [[xmlschema-2]]
See also: dataset modification date

Property: license

RDF Property:dct:license
Definition:This links to the license document under which the distribution is made available.
Range:dct:LicenseDocument
See also: distribution rights, catalog license

Property: rights

RDF Property:dct:rights
Definition:Information about rights held in and over the distribution.
Range:dct:RightsStatement
Usage note:dct:license, which is a sub-property of dct:rights, can be used to link a distribution to a license document. However, dct:rights allows linking to a rights statement that can include licensing information as well as other information that supplements the licence such as attribution.
See also: distribution license, catalog rights

Property: access URL

RDF Property:dcat:accessURL
Definition:A landing page, feed, SPARQL endpoint or other type of resource that gives access to the distribution of the dataset
Domain:dcat:Distribution
Range:rdfs:Resource
Usage note:
  • Use accessURL, and not downloadURL, when it is definitely not a download or when you are not sure whether it is.
  • If the distribution(s) are accessible only through a landing page (i.e. direct download URLs are not known), then the landing page link SHOULD be duplicated as accessURL on a distribution. (see example 4.4)
See alsodistribution download URL

Property: download URL

RDF Property:dcat:downloadURL
Definition:A file that contains the distribution of the dataset in a given format
Domain:dcat:Distribution
Range:rdfs:Resource
Usage note: dcat:downloadURL is a specific form of dcat:accessURL. Nevertheless, DCAT does not define dcat:downloadURL as a subproperty of dcat:accessURL not to enforce this entailment as DCAT profiles may wish to impose a stronger separation where they only use accessURL for non-download locations.
See alsodistribution access URL

Property: byteSize

RDF Property:dcat:byteSize
Definition:The size of a distribution in bytes.
Domain:dcat:Distribution
Range:rdfs:Literal typed as xsd:decimal.
Usage note:The size in bytes can be approximated when the precise size is not known.

Property: media type

RDF Property:dcat:mediaType
Definition:The media type of the distribution as defined by IANA.
Sub property of:dct:format
Domain:dcat:Distribution
Range:dct:MediaTypeOrExtent
Usage note:This property SHOULD be used when the media type of the distribution is defined in IANA, otherwise dct:format MAY be used with different values.
See also: format

Property: format

RDF Property:dct:format
Definition:The file format of the distribution.
Range:dct:MediaTypeOrExtent
Usage note: dcat:mediaType SHOULD be used if the type of the distribution is defined by IANA.

Class: Concept scheme

RDF Class:skos:ConceptScheme
Definition:The knowledge organization system (KOS) used to represent themes/categories of datasets in the catalog.
See also:catalog themes, dataset theme

Class: Concept

RDF Class:skos:Concept
Definition:A category or a theme used to describe datasets in the catalog.
Usage note:It is recommended to use either skos:inScheme or skos:topConceptOf on every skos:Concept used to classify datasets to link it to the concept scheme it belongs to. This concept scheme is typically associated with the catalog using dcat:themeTaxonomy
See also:catalog themes, dataset theme

Class: Organization/Person

RDF Classes:foaf:Person for people and foaf:Organization for government agencies or other entities.
Usage note:FOAF [[!FOAF]] provides sufficient properties to describe these entities.

Acknowledgements

This document contains a significant contribution from Richard Cyganiak. Richard Cyganiak is one of the initiators of the DCAT work and significantly contributed to the work on this specification as it made its way through the W3C process.

The editors would like to thank Vassilios Peristeras for his comments and support for the original DCAT work. Vassilios Peristeras is also one of the initiators of the DCAT work. We would also like to thank Rufus Pollock for his significant input and comments.

This document has benefited from inputs from many members of the Government Linked Data Working Group. Specific thanks are due to Ghislain Atemezing, Martin Alvarez and Makx Dekkers.

Change history

Changes since the W3C Candidate Recommendation 05 November 2013:

Changes since the second W3C Last Call working Draft 01 August 2013:

Changes since W3C Last Call working Draft 12 March 2013: