A flexible open brokering framework supporting distributed semantic discovery

The Discovery and Access Broker (DAB) technology is implemented and deployed in the context of several European Union research projects and international initiatives, such as the Global Earth Observation System of Systems (GEOSS) and WMO Hydrological Observing System (WHOS), to enable discovery and access amongst distributed geospatial data provider services, along the line of fair and open approaches. 

Lately the DAB has been employed in the context of two European Open Science Cloud (EOSC) EU-funded projects FAIR-EASE, and Blue-Cloud 2026, characterized by a strong synergy between them. In FAIR-EASE, a customized DAB instance enables harmonized semantic searches amongst 15 data sources: EuroArgo, the Copernicus Marine Environment Monitoring Service (CMEMS), EasyData, ELIXIR-ENA, EurOBIS, European Environment Agency SDI Catalog, EMODnet, ICOS (Data Portal and SOCAT), Joint Research Centre Data Catalog, SeaDataNet (open datasets and products), US NODC collections, VITO/Copernicus Global Land Services, and WEkEO, totaling 156,000 datasets available for search. 

These services publish data using different service interfaces and data models. The DAB can seamlessly connect to each of them and map results to the interface and data model required by the users, leveraging a flexible and extensible harmonized internal data model based on ISO 19115. 

The broker discovery services are accessible through multiple interfaces, such as OGC CSW, OpenSearch API, and SPARQL endpoint. In particular, the SPARQL endpoint interface follows a linked data approach that is further leveraged by the FAIR-EASE architecture. To realize the SPARQL endpoint, a mapping from ISO 19115 to the FAIR-EASE DCAT profile was implemented. Concept URIs found in the original metadata (e.g., linking parameters, stations, instruments, keywords from online vocabularies) can be easily represented as properties and relations of the mapped FAIR-EASE dataset, supporting further reasoning and harmonized semantic query. 

The connection with the Semantic Analyzer component provided by BODC has been explored and will be the subject of further research. This tool can analyze FAIR-EASE datasets by connecting to the DAB CSW interface, extracting a list of terms and scanning known online vocabularies and ontologies to identify possible concept URIs matches. These URIs can finally replace natural text occurring in the original metadata, enhancing overall semantics and quality.