In the core profile of ISO 19115 geographic extent can be specified either with a bounding box or with a geographic identifier.
Although INSPIRE explicitly requires the use of the former option (i.e., the bounding box), in order to ensure compliance with ISO 19115 core, GeoDCAT-AP should include a mapping for geographic identifiers.
In ISO 19115, the geographic identifier is specified by a “code” (character string), plus an optional “authority”, usually corresponding to the register / code list maintaining the geographic identifier.
Given that:
A. The pattern used in ISO to specify geographic identifiers reflects the one used for keywords from controlled vocabularies.
B. DCAT-AP recommends the use of the Core Location vocabulary (LOCN) to model spatial coverage.
the proposal is as follows:
-
Following point (A), the geographic identifier will be modelled as a skos:Concept, where:
- the code will be specified through skos:prefLabel;
- if the code is associated with an HTTP URI, this will be used as the skos:Concept’s URI;
- the authority as its skos:ConceptScheme.
- Following point (B), the geographic identifier will be associated with the “location” denoting the spatial coverage by using rdfs:seeAlso, i.e., the property that in LOCN is used to specify geographic identifiers (see the relevant section of the LOCN namespace document).
Example (based on NOAA’s wiki page on ISO extents):
[ISO 19139]
<gmd:extent>
<gmd:EX_Extent>
<gmd:geographicElement>
<gmd:EX_GeographicDescription>
<gmd:geographicIdentifier>
<gmd:MD_Identifier>
<gmd:authority>
<gmd:CI_Citation>
<gmd:title>
<gco:CharacterString>NASA/GCMD Location Keywords</gco:CharacterString>
</gmd:title>
<gmd:date>
<gmd:CI_Date>
<gmd:date>
<gco:Date>2009-01-01</gco:Date>
</gmd:date>
<gmd:dateType>
<gmd:CI_DateTypeCode codeList="http://www.isotc211.org/2005/resources/Codelist/
gmxCodelists.xml#CI_DateTypeCode" codeListValue="revision">revision</gmd:CI_DateTypeCode>
</gmd:dateType>
</gmd:CI_Date>
</gmd:date>
</gmd:CI_Citation>
</gmd:authority>
<gmd:code>
<gco:CharacterString>Location > Geographic Region > Global Ocean</gco:CharacterString>
</gmd:code>
</gmd:MD_Identifier>
</gmd:geographicIdentifier>
</gmd:EX_GeographicDescription>
</gmd:geographicElement>
</gmd:EX_Extent>
<gmd:extent>
[GeoDCAT-AP]
<dct:spatial>
<dct:Location>
<rdfs:seeAlso>
<skos:Concept>
<skos:prefLabel xml:lang="en">Location > Geographic Region > Global Ocean</skos:prefLabel>
<skos:inScheme>
<skos:ConceptScheme>
<rdfs:label xml:lang="en">NASA/GCMD Location Keywords</rdfs:label>
<dct:modified rdf:datatype="http://www.w3.org/2001/XMLSchema#date">2009-01-01</dct:modified>
</skos:ConceptScheme>
</skos:inScheme>
</skos:Concept>
</rdfs:seeAlso>
</dct:Location>
</dct:spatial>
Comments
Comment via the mailing list:
http://joinup.ec.europa.eu/mailman/archives/dcat_application_profile-geo/2015-May/000070.html
Udo Einspanier
Tue May 19 12:36:08 CEST 2015
Dear Andrea,
+1, the proposal is fine with me. But I have a more general question that also concerns this point. In the DCAT-AP revision draft it says for dct:spatial that one of the three specified controlled vocabularies (MDR countries, MDR places, geonames.org) MUST be used for this property. Would this proposal still be compatible with that requirement? Or is this only relevant for cases where new metadata is created?
Best regards,
Udo
Revised proposal, based on what decided during the 4th GeoDCAT-AP WG meeting.
During the 4th WG meeting of 20 May 2015, it was decided by vote that the proposed for encoding ISO19115 Geographic Identifier is to use rdfs:seeAlso, as also suggested in the Core Location Vocabulary (LOCN), with a URI: <dct:spatial rdf:resource="URI"/>, with the change that http URIs, rather than blank notes, are used in the example is accepted. A note on URIs should be added.
There is an explanation of the decision taken in the last version of the GeoDCAT-AP specifications. This can be completed with the issue on how to encode or represent a geographic bounding box or geometry:
In the core profile of ISO 18115, spatial coverage can be specified either with a bounding box (a geometry) or a geographic identifier. INSPIRE is more restrictive, in that it requires to use a bounding box.
Based on that, GeoDCAT-AP models spatial coverage as follows:
The following example shows how to specify the spatial coverage.
# Resource metadata in GeoDCAT-AP using a geographic bounding box. This example uses multiple encodings, namely, the# recommended ones (WKT and GML), plus GeoJSON. To denote the datatype of the GeoJSON literal, the URL of the corresponding
# IANA media type.
[] dct:spatial [ a dct:Location ;
locn:geometry "POLYGON((-10.58 70.09,34.59 70.09,34.59 34.56,-10.58 34.56,
-10.58 70.09))"^^gsp:wktLiteral ;
locn:geometry "<gml:Envelope srsName=\"http://www.opengis.net/def/crs/OGC/1.3/CRS84\">
<gml:lowerCorner>34.56 -10.58</gml:lowerCorner>
<gml:upperCorner>70.09 34.59</gml:upperCorner>
</gml:Envelope>"^^gsp:gmlLiteral ] ;
locn:geometry "{\"type\":\"Polygon\",\"crs\":{\"type\":\"name\",\"properties\":{\"name\":\"urn:ogc:def:crs:OGC:1.3:CRS84\"}},
\"coordinates\":[[[-10.58,70.09],[34.59,70.09],[34.59,34.56],[-10.58,34.56],[-10.58,70.09]]]
}"^^<https://www.iana.org/assignments/media-types/application/vnd.geo+json> ].
# Resource metadata in GeoDCAT-AP using a geographic identifier
#If a URI is used for the geographic identifier (recommended)
[] dct:spatial <http://publications.europa.eu/resource/authority/country/NLD>.
#If no URI is used for the geographic identifier
[] dct:spatial [
skos:preflabel "Netherlands"@en;
skos:prefLabel "Nederland"@nl;
skos:inScheme [
dct:title "Countries Authority Table"@en;
dct:modified "2009-01-01"^^xsd:date
]
].
<!-- Resource metadata in ISO19139 using a geographic bounding box --><gmd:MD_Metadata>
...
<gmd:identificationInfo>
<gmd:MD_DataIdentification>
<gmd:extent>
<gmd:EX_Extent>
<gmd:geographicElement>
<gmd:EX_GeographicBoundingBox>
<gmd:extentTypeCode>
<gco:Boolean>true</gco:Boolean>
</gmd:extentTypeCode>
<gmd:westBoundLongitude>
<gco:Decimal>-9.227701</gco:Decimal>
</gmd:westBoundLongitude>
<gmd:eastBoundLongitude>
<gco:Decimal>2.687637</gco:Decimal>
</gmd:eastBoundLongitude>
<gmd:southBoundLatitude>
<gco:Decimal>49.83726</gco:Decimal>
</gmd:southBoundLatitude>
<gmd:northBoundLatitude>
<gco:Decimal>60.850441</gco:Decimal>
</gmd:northBoundLatitude>
</gmd:EX_GeographicBoundingBox>
</gmd:geographicElement>
</gmd:EX_Extent>
</gmd:extent>
</gmd:MD_DataIdentification>
</gmd:identificationInfo>
...
</gmd:MD_Metadata>