How to model Dataset series?
Issue
During the revision process of DCAT-AP in 2015, it was noted that the base specification of DCAT at W3C only considers relationships between a catalogue and the datasets described in the catalogue, and between a dataset and the distributions that represent the manifestations of the dataset.
The base specification is silent on any relationships between datasets, while many such relationships may exist. Two types of relationships are common, namely time series, e.g. annual budget files, or relationships in a geographic dimension, e.g. data from weather sensors in various locations that are combined into data for a wider geographic area.
Additionally, DCAT-AP allows relating datasets as ‘versions’ using dct:hasVersion/dct:isVersionOf but it is not clearly described in which cases to use these properties.
Current situation
In real-world implementations, these relationships may be modelled in different ways. In some implementations, (time) series are modelled as Distributions of a single Dataset; in others, as separate Datasets with or without links between them.
This leads to situations where different providers may apply different approaches to very similar data which may not always be understandable for users and may make comparison of data across data providers difficult.
Recommendation
Based upon consideration of existing practice and further discussion, the following approaches are suggested:
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Rationale
In the absence of consensus on how to model temporal or spatial series, the recommendation intends to give advice that considers the issue from the user perspective and may lead to a more coherent environment that is understandable to users, while retaining flexibility in the approach followed by data providers.
Example
Annual budget data - focus on individual members of the series
<rdf:Description rdf:about="http://dataportal.example.eu/datasets/EUBudget"> <rdf:type rdf:resource="http://www.w3.org/ns/dcat#Dataset"/> <dct:type rdf:resource="http://inspire.ec.europa.eu/metadata-codelist/ResourceType/series"/> <dct:title xml:lang="en">EU Budget Data</dct:title> <dct:hasPart rdf:resource="http://dataportal.example.eu/datasets/EUBudget2015"/> <dct:hasPart rdf:resource="http://dataportal.example.eu/datasets/EUBudget2016"/> </rdf:Description> <rdf:Description rdf:about="http://dataportal.example.eu/datasets/EUBudget2015"> <rdf:type rdf:resource="http://www.w3.org/ns/dcat#Dataset"/> <dct:title xml:lang="en">EU Budget 2015</dct:title> <dct:isPartOf rdf:resource="http://dataportal.example.eu/datasets/EUBudget"/> </rdf:Description> <rdf:Description rdf:about="http://dataportal.example.eu/datasets/EUBudget2016"> <rdf:type rdf:resource="http://www.w3.org/ns/dcat#Dataset"/> <dct:title xml:lang="en">EU Budget 2016</dct:title> <dct:isPartOf rdf:resource="http://dataportal.example.eu/datasets/EUBudget"/> </rdf:Description> |
Annual budget data - focus on the collection
<rdf:Description rdf:about="http://dataportal.example.eu/datasets/EUBudget"> <rdf:type rdf:resource="http://www.w3.org/ns/dcat#Dataset"/> <dct:title xml:lang="en">EU Budget Data</dct:title> <dcat:distribution rdf:resource="http://dataportal.example.eu/datasets/EUBudget2015"/> <dcat:distribution rdf:resource="http://dataportal.example.eu/datasets/EUBudget2016"/> </rdf:Description> <rdf:Description rdf:about="http://dataportal.example.eu/datasets/EUBudget2015"> <rdf:type rdf:resource="http://www.w3.org/ns/dcat#Distribution"/> <dct:title xml:lang="en">EU Budget 2015</dct:title> </rdf:Description> <rdf:Description rdf:about="http://dataportal.example.eu/datasets/EUBudget2016"> <rdf:type rdf:resource="http://www.w3.org/ns/dcat#Distribution"/> <dct:title xml:lang="en">EU Budget 2016</dct:title> </rdf:Description> |