Geometry Chapter 7 Vocabulary

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DCAT2 supersedes DCAT [VOCAB-DCAT-20140116], but it does not make it obsolete. DCAT 2 maintains the DCAT namespace as its terms preserve backward compatibility with DCAT [VOCAB-DCAT-20140116]. DCAT 2 relaxes constraints and adds new classes and properties, but these changes do not break the definition of previous terms.

Any new implementation is expected to adopt DCAT 2, while the existing implementations do not need to upgrade to it, unless they want to use the new features. In particular, current DCAT deployments that do not overlap with the DCAT 2 new features (e.g., data services, time and space properties qualified relations, packaging) don't need to change anything to remain in conformance with DCAT 2.

DCAT enables a publisher to describe datasets and data services in a catalog using a standard model and vocabulary that facilitates the consumption and aggregation of metadata from multiple catalogs. This can increase the discoverability of datasets and data services. It also makes it possible to have a decentralized approach to publishing data catalogs and makes federated search for datasets across catalogs in multiple sites possible using the same query mechanism and structure. Aggregated DCAT metadata can serve as a manifest file as part of the digital preservation process.

This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at

This document defines a major revision of the original DCAT vocabulary ([VOCAB-DCAT-20140116]) in response to new use cases, requirements and community experience since that publication. This revision extends the original DCAT standard in line with community practice while supporting diverse approaches to data description and dataset exchange. The main changes to the DCAT vocabulary have been:

This new version of the vocabulary updates and expands the original but preserves backward compatibility. A full list of the significant changes (with links to the relevent github issues) is described in D. Change history.

The exit criteria for CR focussed on v2 new features that replicate features that were included in application profiles of v1 as a way of remedying missing and necessary elements. The exit criteria also included recent commitments by organisations such as EC Joinup to adopt the DCAT v2 model in their work. Implementation will be evidenced by showing use of the new properties/classes (or terms with equivalent meaning) in implementations of catalogs.

Issues, requirements, and features that have been considered and discussed by the Data eXchange Working Group but have not been addressed due to lack of maturity or consensus are collected in GitHub. Those believed to be a priority for a future release are in the milestone DCAT Future Priority Work.

The original DCAT vocabulary was developed and hosted at the Digital Enterprise Research Institute (DERI), then refined by the eGov Interest Group, and finally standardized in 2014 [VOCAB-DCAT-20140116] by the Government Linked Data (GLD) Working Group.

This revised version of DCAT was developed by the Dataset Exchange Working Group in response to a new set of Use Cases and Requirements [DCAT-UCR] gathered from peoples' experience with the DCAT vocabulary from the time of the original version, and new applications that were not considered in the first version. A summary of the changes from [VOCAB-DCAT-20140116] is provided in D. Change history.

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 the externally-defined terms are included in the DCAT vocabulary for convenience, while authoritative definitions are available in the normative references. Changes to definitions in the references, if any, supersede the summaries given in this specification. Note that conformance to DCAT ( 4. Conformance) concerns usage of only the terms in the DCAT vocabulary specification, so possible changes to other external definitions will not affect the conformance of DCAT implementations.

This document has been reviewed by W3C Members, by software developers, and by other W3C groups and interested parties, and is endorsed by the Director as a W3C Recommendation. It is a stable document and may be used as reference material or cited from another document. W3C's role in making the Recommendation is to draw attention to the specification and to promote its widespread deployment. This enhances the functionality and interoperability of the Web.

This document was produced by a group operating under the W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.

Sharing data resources among different organizations, researchers, governments and citizens requires the provision of metadata. This is irrespective of the data being open or not. DCAT is a vocabulary for publishing data catalogs on the Web, which was originally developed in the context of government data catalogs such as data.gov and data.gov.uk, but it is also applicable and has been used in other contexts.

This revision of DCAT has extended the previous version to support further use cases and requirements [DCAT-UCR]. These include the possibility of cataloging other resources in addition to datasets, such as data services. The revision also supports describing relationships between datasets as well as between datasets and other cataloged resources. Guidance on how to document licenses and rights statements associated with the cataloged items is provided.

DCAT provides RDF classes and properties to allow datasets and data services to be described and included in a catalog. The use of a standard model and vocabulary facilitates the consumption and aggregation of metadata from multiple catalogs, which can:

Data described in a catalog can come in many formats, ranging from spreadsheets, through XML and RDF to various specialized formats. DCAT does not make any assumptions about these serialization formats of the datasets but it does distinguish between the abstract dataset and its different manifestations or distributions.

Data is often provided through a service which supports selection of an extract, sub-set, or combination of existing data, or of new data generated by some data processing function. DCAT allows the description of a data access service to be included in a catalog.

Complementary vocabularies can be used together with DCAT to provide more detailed format-specific information. For example, properties from the VoID vocabulary [VOID] can be used within DCAT to express various statistics about a dataset if that dataset is in RDF format.

This document does not prescribe any particular method of deploying data catalogs expressed in DCAT. DCAT information can be presented in many forms including RDF accessible via SPARQL endpoints, embedded in HTML pages as [HTML-RDFa], or serialized as RDF/XML [RDF-SYNTAX-GRAMMAR], [N3], [Turtle], [JSON-LD] or other formats. Within this document the examples use [Turtle] because of its readability.

The original Recommendation [VOCAB-DCAT-20140116] published in January 2014 provided the basic framework for describing datasets. It made an important distinction between a dataset as an abstract idea and a distribution as a manifestation of the dataset. Although DCAT has been widely adopted, it has become clear that the original specification lacked a number of essential features that were added either through the mechanism of a profile, such as the European Commission's DCAT-AP [DCAT-AP], or the development of larger vocabularies that to a greater or lesser extent built upon the base standard, such as the Healthcare and Life Sciences Community Profile [HCLS-Dataset], the Data Tag Suite [DATS] and more. This revision of DCAT has been developed to address the specific shortcomings that have come to light through the experiences of different communities, the aim being to improve interoperability between the outputs of these larger vocabularies. For example, in this new DCAT version we provide classes, properties and guidance to address identifiers, dataset quality information, and data citation issues.

This revision includes re-writing of the specification throughout. Significant changes from the 2014 Recommendation are marked within the text using "Note" sections, as well as being described in D. Change history.

A DCAT profile is a specification for a data catalog 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:

Along with the rest of 5. Vocabulary overview, this diagram is non-normative. Furthermore, while the diagram uses UML-style class notation it should be interpreted following the usual RDF open-world assumptions around the presence/absence of properties, relationships, and their cardinality. The properties shown in each class reflect those specified in the descriptions of classes in 6. Vocabulary specification. To assist in understanding the full scope of each class, properties are copied down from each '::super-class'. Cardinalities are shown in a few places to reinforce expectations, but these are not axiomatized or enforced in any way by this (normative) recommendation.

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 serializations or formats". A dataset is a conceptual entity, and can be represented by one or more distributions that serialize the dataset for transfer. Distributions of a dataset can be provided via data services.

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