uData as built-in RDF support allowing to both expose and harvest RDF metadata. It uses the Data Catalog Vocabulary (or DCAT) as base vocabulary.


udata exposes instance metadata through different RDF endpoints and try to follow some best practices.

All relative URLs are relative to the udata instance root

Content Negociation

The following format supported (default in bold):

Format Extension MIME type
RDF/XML xml, rdf application/rdf+xml, application/xml
Turtle ttl text/turle, application/x-turtle
Notation3 n3 text/n3
JSON-LD jsonld, json application/ld+json, application/json
N-Triples nt application/n-triples
TriG trig application/trig

Each endpoint is available through a generic URL which perform content negociation and redirect to a set of format specific URLs. The default format is JSON-LD.


Dataset are available through the following URL:


where id is dataset identifier on the udata instance.

This URL performs content negociation and redirect to:


The dataset pages serve as identifier and perform content negociation too, so the following URLs will all redirect to the same RDF endpoint:


Dataset is exposed as a DCAT Dataset, Resource as DCAT Distribution and fields are mapped according to:

Dataset dcat:Dataset notes
id dct:identifier
title dct:title
description dct:description
tags dct:keyword
created_at dct:issued
last_modified dct:modified
resources dcat:distribution
temporal_coverage dct:temporal Uses schema.org startDate and endDate
frequency dct:accrualPeriodicity Frequencies without Dublin Core equivalent are mapped to the closest one
license dct:license + dct:right License URL in dct:license and license label in dct:right
Resource dcat:Distribution notes
id dct:identifier
title dct:title
description dct:description
url dcat:downloadURL as URI reference
permanent url dcat:accessURL as URI reference
published dct:issued
last_modified dct:modified
format dct:format
mime dcat:mediaType
filesize dcat:bytesSize
checksum spdx:checksum
TemporalCoverage dct:PeriodOfTime
start schema:startDate
end schema:endDate
Checksum spdx:Checksum
type spdx:algorithm
value spdx:checksumValue


The site catalog is exposed through:


and perform content negociation to


It is exposed as a DCAT Catalog and a Hydra Collection This allows pagination through the hydra:PartialCollectionView class.


There is a work in progress Dataportal specification but as many site already uses this formalism, the catalog is also available (as a redirect) on the following URL:


where format is one of supported format extension.

JSON-LD context

To reduce payload and increase human readbility, udata exposes a JSON-LD context and uses it in its serialization. This context is available on:



udata can harvest other RDF/DCAT enabled data portals with the DCAT Harvester.


The udata rdf implementation and its harvester were created using these references:

The used namespaces are: