Author: Štěpán Kafka (Help Service Remote Sensing)
DCAT represents metadata format proposed for European portals based on principles of semantic web [1, 2]. In the framework of ISA Action 1.17 (ARe3NA), an alignment exercise has been carried out between INSPIRE metadata and DCAT-AP. The motivation for this work is twofold:
GeoDCAT-AP is an extension of DCAT-AP for describing geospatial datasets, dataset series, and services. It provides an RDF syntax binding for the union of metadata elements defined in the core profile of ISO 19115:2003 and those defined in the framework of the INSPIRE Directive. Its basic use case is to make spatial datasets, data series, and services searchable on general data portals, thereby making geospatial information better searchable across borders and sectors. This can be achieved by the exchange of descriptions of data sets among data portals.
GeoDCAT –AP is still in under development led by Joint Research Centre. Currently draft version 7 is available.
The background and preliminary results of this work has been presented at the INSPIRE 2014 Conference.
MICKA metadata catalogue implementation
MICKA is spatial metadata catalogue / editor maintained by HSRS. It supports CSW 2.0.2 / INSPIRE discovery service. Besides CSW 2.0.2 / ISO-AP 1.0 profile it supports many output formats as HTML, PDF, JSON, GeoRSS, Atom, KML, OAI_PMH and OAI_MARC21. Internally the metadata are stored in ISO 19139 format. DCAT RDF-XML output was implemented with XSL template according to rules defined in .
- There are several methods for automatically adding URIs for keywords stored in XML as strings with mapping to original thesauri (e.g. GEMET) and INSPIRE registry (URI forms of INSPIRE data themes mapping) .
- MICKA does not support SPARQL endpoint currently.
Picture 1: MICKA search form
Picture 2. MICKA Search result with added link to DCAT – RDF metadata representation
Picture 3. W3C Validator results for CKAN RDF-XML provided by MICKA.
CKAN is very popular catalogue used for Open data publication. Currently it supports harvesting from OGC Catalogues (CSW 2.0.2) including ISO AP 1.0, but the harvested metadata does not cover all INSPIRE required metadata elements. Also visualisation of metadata was not comfortable. RDF output is available but not fully compatible with DCAT-AP. SPARQL endpoint is not available.
For DCAT-AP INSPIRE profile these problems should be solved:
- Extend the CKAN harvesting to support all INSPIRE metadata elements.
- Provide user friendly visual representation of imported INSPIRE metadata in CKAN.
- Support DCAT compatible output according to [2, 3].
- Provide SPARQL endpoint
- Extension module was developed in addition to existing harvester to import additional INSPIRE metadata to DCAT (See picture 4.). It is based on XSL templates so simply configurable without need to change the code.
- Extension for metadata visualization was developed using CKAN Jinja2 templating system plus Python background. (Picture 5). This module takes metadata saved in the database and transform them into more readable form.
- The template for Geo DCAT-AP output was developed.
- We decided not to provide the solution for SPARQL endpoint in the DCAT but if it is needed, we will use existing software – Virtuoso server, where the data may be replicated to.
Picture 4: Part of imported INSPIRE metadata in CKAN – extended by metadata party and resource identifier. Original CKAN formatting
Picture 5: Improved metadata display with using of our own extension.
Picture 6: INSPIRE DCAT-AP (GeoDCAT) output example (part)
Czech national portal implementation
On the Czech national INSPIRE portal the DCAT-AP representation of the INSPIRE metadata is generated on-the-fly supporting e.g. keywords traslation to URIs.
- MICKA metadata catalogue: http://dev.bnhelp.cz/projects/metadata/trunk/?request=GetRecords&format=text/html&language=cze&query=&sortby=
- MICKA generated RDF: http://dev.bnhelp.cz/projects/metadata/trunk/csw/?service=CSW&request=GetRecordById&id=XXXX&outputschema=http://www.w3.org/ns/dcat#
- Customised HTML visualisation of imported INSPIRE metadata: http://ckan.ccss.cz/dataset/database-of-mineral-resources-industrial-minerals-and-rocks
- DCAT-AP RDF output: http://ckan.ccss.cz/dataset/database-of-mineral-resources-industrial-minerals-and-rocks.rdf
- DCAT viewer: http://idi.fundacionctic.org/dcat-viewer/dcat-viewer?documentUri=http%3A%2F%2Fckan.ccss.cz%2Fdataset%2Fdatabase-of-mineral-resources-industrial-minerals-and-rocks.rdf&mimetype=application%2Frdf%2Bxml
- Czech national portal – metadata client: http://geoportal.gov.cz/web/guest/catalogue-client
 Data Catalog Vocabulary (DCAT), W3C Recommendation 16 January 2014. http://www.w3.org/TR/vocab-dcat/
 DCAT application profile for data portals in Europe. 14 August 2014. https://joinup.ec.europa.eu/asset/dcat_application_profile/description
 INSPIRE profile of DCAT-AP – Extended version, https://ies-svn.jrc.ec.europa.eu/projects/metadata/wiki/INSPIRE_profile_of_DCAT-AP_-_Extended_version
 INSPIRE Registry. http://inspire.ec.europa.eu/registry/