[Issue #10] Add properties dct:format and dcat:mediaType for dcat:DataService?

Published on: 24/06/2021

Norwegian Digitalisation Agency representative raised the issue regarding the formats/mediaTypes a DataService may support in BregDCAT-AP, as this is one of the  main considerations when deciding whether a DataService is (re)usable or not.  

In the current version of BRegDCAT-AP, dcat:DataService doesn’t have properties dct:format and dcat:mediaType the way dcat:Distribution has. Possible ways to describe formats/mediaTypes of a DataService are thus: 

  1. Using dcat:DataService/dcat:endpointDescription. The main disadvantage is that it doesn’t necessarily ensure a standardized way of expressing formats and mediaTypes, which makes it impossible to e.g., sort/query DataServices according to formats/mediaTypes. 
  2. Using dcat:DataService/dcat:servesDataset -> dcat:Dataset/dcat:distribution -> dcat:Distribution/dct:format (or dcat:Distribution/dcat:mediaType). The main disadvantage is the _unnecessary_ overhead in creating and maintaining all those extra Distributions (and Datasets). 
    1. Since the multiplicities for dcat:Distribution/dct:format and dcat:Distribution/dcat:mediaType are both 0..1 in BRegDCAT-AP, one has to create several Distributions in order to express that a DataService/API may support several different formats/mediaTypes. 

There are real cases where DataServices provide data in several different formats/mediaTypes (e.g., all 6 standard serializations of RDF), and which are not associated to any Distribution nor Dataset. 

Norwegian Digitalisation Agency proposed to  add the following properties  to dcat:DataService: 

  • recommended, format, dct:format, 0..n, range dct:MediaTypeOrExtent, EU File Type must be used
  • optional, media type, dcat:mediaType, 0..n , range dct:MediaType, IANA Media Types must be used

Note: Those new properties are same as the corresponding ones in dcat:Distribution, except for the multiplicities which are 0..n for both here in dcat:DataService since a DataService/API may support several different formats/mediaTypes

Options to discuss:

  • Add properties dct:format and dcat:mediaType to dcat:DataService
  • Other possible ways to address this issue
  • Examples, etc.