Combining virtual graphs and the other graphs


We have several named graphs (triples physically loaded in the triple store) and we have created one virtual graph on a relational database. As the information in the virtual graph is completing what we have in one of the named graph, we need to combine both graphs in our queries.

If I am using the following syntax, I am able to combine the graphs and get all the triples.

select *
where {
{graph virtual://drm { ?p ?o }}
{graph { ?p ?o }} }

But if I am using that other syntax, only the triples of the non virtual graph are returned. And there is a warning in the log.

select *
from virtual://drm
where { ?p ?o }

WARN 2019-06-26 13:49:35,916 [stardog-user-19] com.complexible.stardog.plan.optimizer.VirtualGraphProcessor:getDefaultVirtualGraph(119): There can only be a single virtual graph in the query dataset: {} [virtual://drm,]

  • Is there a way to make something like the second syntax working?
  • And maybe also to add a second virtual graph in the query?
  • Could that second virtual graph be non relational (MongoDB or Cassandra)?


Hi Daniel,

We are working on this right now and will release it in 1-2 months. You will be able to include any number and type of virtual graphs in the dataset specification.


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