The OGSA-DAI RDF resource is an extension to OGSA-DAI which adds a new data resource to the framework. The RDF resource extends the existing data resources (relational and XML databases, indexed files) with a resource that provides access to RDF datasets. The access is done either by connecting directly to the database containing the RDF triples (via Jena SDB) or connecting to a SPARQL endpoint at the RDF dataset side. In the figure below it is shown the extension to OGSA-DAI with the new data resource (plus a new resource in development that accesses a RDB2RDF processor).

The RDF resource only provides connection facilities to the data sources. The actual data retrieval and processing is done by complementary activities to this resource. These activities contact the RDF resource getting the connection information. With this information they query the RDF repository, wither using an available SPARQL endpoint or directly querying the database containing the RDF triples. The framework chosen to connect to the RDF stores is Jena. Once the query has been done its results are converted by these activities to the OGSA-DAI tuple format. This format (<value1, value2, …> allows to connect the results of the SPARQL with the results from other queries to other data resources. The source code of this extension can be found in the OGSA-DAI SVN at Sourceforge . The architecture is depicted in the following image.

Currently this extension is being used in the ADMIRE project  and by the Sciences and Technologies Facilities Council in the UK.