Grasp binding to Virtuoso / DBpedia

[cblakeley]

Hello,

This pull request allows Grasp to work with a Virtuoso SPARQL endpoint and consequently with DBpedia. The changes address issue #11.

Without this change, Grasp issues CONSTRUCT queries to the SPARQL backend using POST with URL-encoded parameters and Content-Type: application/x-www-form-urlencoded, as described in SPARQL 1.1 Protocol 2.1.2: query via POST with URL-encoded parameters. The patch modifies Grasp to POST CONSTRUCT queries using Content-Type: application/sparql-query as per SPARQL 1.1 Protocol 2.1.3: query via POST directly.

Two simple GraphQL query examples have also been added to demonstrate Grasp querying DBpedia. Please see README_OPL.md for details.

Thanks,
Carl Blakeley
OpenLink Software

[kidehen]

It also extends Grasp to other SPARQL endpoints across the LOD Cloud Knowledge Graph :)

[ktym]

Thank you for your investigation. We'll look into it.