Making geospatial information available through open data portals increases its potential to be found and consumed not only in the geospatial, but also in other sectors (e.g. eGovernment). In the context of the ARE3NA Action funded by the ISA Programme, the Joint Research Centre has developed an experimental tool to convert metadata from ISO 19115/19139, the standards widely used in the geospatial domain, to DCAT-AP or its geospatial extension GeoDCAT-AP, the standards used for open data portals in Europe. 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.
What does the conversion tool do?
The tool provides a service that is capable of retrieving metadata from an OGC Catalogue Service for the Web (CSW) server and converting it into the WC3’s linked data’s Resource Description Framework (RDF) in one of several serialisations according to either the DCAT-AP or GeoDCAT-AP.
Why a conversion tool for (Geo)DCAT-AP?
To date, search services for spatial information, such as INSPIRE discovery services, are often based on the CSW standard (e.g. CSW HTTP Request). The CSW provides an HTTP interface allowing machine readable metadata to be requested from a server in ISO19139 xml format. The GeoDCAT-AP specification provides an alternative RDF syntax for metadata according to the INSPIRE Metadata Regulation and the ISO19115 Core profile. Providing geospatial metadata in this additional syntax can aid data discovery with a wider group of potential data users. The conversion tool allows the automatic conversion with very little additional investment from data providers.
How does it work?
The Joint Research Centre developed in the context of the ARE3NA ISA Action an XSLT stylesheet to do an automatic conversion from ISO 19139 to (Geo)DCAT-AP. The experimental conversion tool for GeoDCAT-AP uses the standardised CSW HTTP Request interface (using the GetRecords or GetRecordById operations) to retrieve descriptive metadata in ISO 19139 format. Subsequently, it uses the GeoDCAT-AP XSLT stylesheet to transform ISO 19139 records into (Geo)DCAT-AP. Alternatively, the tool works also on static files including metadata records.
About the output format
Currently, the conversion tool supports different RDF serialisations of DCAT-AP and GeoDCAT-AP - more precisely, RDF/XML, Turtle, N3, N-Triples and JSON-LD. There are also plans to add HTML+RDFa, starting from September.
This is the very first version of the prototype and some features requires further refinements. In particular, error handling and content negotiation will need to be addressed in September. The prototype is not meant to be used for converting massive amounts of records. It is, instead, intended to be a proof-of-concept for the definition of a reference CSW implementation of GeoDCAT-AP, based on the standard CSW interface.
Do you want to know more?
If you would like to know more about this work, please contact the ARE3NA Team: email@example.com.