Hello,

With the new repository the clerezza rdf commons previously in the commons
sandbox are now at:

https://git-wip-us.apache.org/repos/asf/clerezza-rdf-core.git

I will compare that code with the current status of the code in the
incubating rdf-commons project in a later mail.

Now I would like to point to your attention a big step forward towards
CLEREZZA-856. The impl.sparql modules provide an implementation of the API
on top of a SPARQL endpoint. Currently it only supports read access. For
usage example see the tests in
/src/test/java/org/apache/commons/rdf/impl/sparql (
https://git-wip-us.apache.org/repos/asf?p=clerezza-rdf-core.git;a=tree;f=impl.sparql/src/test/java/org/apache/commons/rdf/impl/sparql;h=cb9c98bcf427452392e74cd162c08ab308359c13;hb=HEAD
)

The hard part was supporting BlankNodes. The current implementation handles
them correctly even in tricky situations, however the current code is not
optimized for performance yet. As soon as BlankNodes are involved many
queries have to be sent to the backend. I'm sure some SPARQL wizard could
help making things more efficient.

Since SPARQL is the only standardized methods to query RDF data, I think
being able to façade an RDF Graph accessible via SPARQL is an important
usecase for an RDF API, so it would be good to also have an SPARQL backed
implementation of the API proposal in the incubating commons-rdf repository.

Cheers,
Reto

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