Catalog as subclass of Dataset - RE: Fwd: Feedback for https://w3c.github.io/dxwg/dcat/

Thanks Melanie –

On item 2 I refer you to Figure 1 in section 5 of the draft rec https://w3c.github.io/dxwg/dcat/#vocabulary-overview also available directly from https://w3c.github.io/dxwg/dcat/UML/DCAT-summary.png


A Catalog has one or more entries, which are dcat:Resources, and a registration record – the dcat:CatalogRecrod – for each entry.

Specialized predicates – dcat:dataset, dcat:service and dcat:catalog are defined as sub-properties of dct:hasPart, with the range constrained either a dcat:Dataset, a dcat:DataService, or a dcat:Catalog, respectively. These are generally preferred to the vanilla dct:hasPart predicate.

A Catalog is thus a kind of Dataset, whose members are dcat:Resources (i.e. descriptions of datasets, dataservices, and other catalogs), and in particular which inherits all the properties that can be used to describe any other Dataset and dcat:Resource, such as accrualPeriodicity, modification date, contactPoint, etc.

We realised that this sub-class relationship existed when we were looking at the proposition that a catalog might have other catalogs as members, in order to create a federated catalog.

Note also that the ‘Catalog’ is the _content_ of a catalog service, which is a special kind of data-service, probably a data discovery service.

Simon


From: Melanie Barlow [mailto:melanie.barlow@ands.org.au]
Sent: Wednesday, 15 August, 2018 12:36
To: public-dxwg-comments@w3.org
Subject: Re: Fwd: Feedback for https://w3c.github.io/dxwg/dcat/


Hi Simon,
1.       There is no requirement that any particular end-point (URL) may only provide one service type. Sub-classes of a common parent are not disjoint unless said so. The RDF open-world-assumption says that anything that isn't explicitly stated is undefined, so modelling is generally permissive rather than exclusive.

Ok, thank you for that confirmation.
2.       Catalog and CatalogRecord have not been changed compared with DCAT 2014, except that we now recognise that a Catalog is a kind of Dataset, composed of Dataset and DataService descriptions.

Ok, yes, that's the part that I am particularly interested in: considering it as a type of Dataset, and understanding the history behind the overlap of members between it and Resource.
3.       The topic of Related Datasets (and relationships between catalogued resources in general) is the topic of https://github.com/w3c/dxwg/issues/81 which has not yet been resolved.

Thank you, I will take a look.

Melanie