Info: on distribution / dataservice mapping rules

[joachimnielandt]

The following describes the mappings to dcat distributions and dataservices, deployed in Flanders. This ticket serves to share the approach and boost a discussion around the core mapping of ISO INSPIRE to GeoDCAT-AP.

Below there are two rules for Distributions: the first is the obvious case where the data is shared as a downloadable file, the second corresponds to a more interactive distribution where an API must be consumed to download the whole dataset. The third rule is about Data Services.

Observe that in our case the INSPIRE simplication for metadata was not performed for our ISO INSPIRE metadata. Consequently the Data Services do not have to be derived from transferOptions/OnlineResources embedded in a Dataset. They are independently documented. And this structure closely corresponds to the DCAT resources. Therefore the challenge is more situated at creating proper interlinked DCAT resources of datasets, distributions and data services.

Create dcat distribution (downloadable)

for MD_ScopeCode = 'dataset'
map each gmd:transferOptions > gmd:CI_OnlineResource
if protocol in ['WWW:DOWNLOAD-1.0-ftp--download', 'WWW:DOWNLOAD-1.0-http--download', 'LINKdownload-store']

gmd:CI_OnlineResource/gmd:linkage/gmd:URL is mapped to the required dcat:accessURL

ISO	GeoDCAT-AP VL
Name	title
Description	description
Linkage	accessURL
Format	format

Formats are taken from the list provided by the EU Publications Office (https://op.europa.eu/en/web/eu-vocabularies/dataset/-/resource?uri=http://publications.europa.eu/resource/dataset/file-type), also discussed in #119.

Create dcat distribution (specific layer of downloadable service)

for MD_ScopeCode = 'dataset'
map each gmd:transferOptions > gmd:CI_OnlineResource
if protocol in ['getMap/getTile', 'getFeature/getCoverage']

Attribute	Description
accessURL	(GDI-Vlaanderen) limited URL
accessService	Dataservice that responds to the query
alternativeIdentifier (adms:identifier)	The parameter that identifies the distribution data in a geoservice
description	Default message: The accessURL refers to a limited set of data, as defined in the GDI-Vlaanderen terms.

Example alternativeIdentifier:

<ex:distributie1>adms:identifier[
_:skos:notation"<laag>" ^^ <wms:Layer>.
]

For the various service types, the following literal type (?) is used:

Distribution	Service entity	Literal type
WMS	Layer	http://www.opengis.net/wms#Layer
WMTS	Layer	http://schemas.opengis.net/wmts#Layer (not resolvable)
WFS	Feature	http://www.opengis.net/wfs#FeatureType
WCS	Coverage	http://www.opengis.net/wcs#CoverageDescription

Example use cases:

• third party application uses the ISO distribution (that offers the GetMap protocol) to refer to the map visualisation.
• a catalog user wants to integrate with data-offering applications, e.g., visualisations, based on the description of a distribution / dataset.

Reasoning:

• An ISO distribution with protocol GetMap refers to a specific layer in a dataservice.
• This aligns with our download / file interpretation of distributions.
• The layer parameter determines the complete content of the dataset.
• Downloadability is still possible, although inefficient.

Create dcat dataservice

for each type (WMS, WFS, ...) of MD_ScopeCode = service
map 1 service operation to dcat:endpointURL and dcat:endpointDescription

[uvoges]

This is arelated issue I guess: #123