Federated DESCRIBE with sub-SELECT

[Martynas Jusevičius]

Hey list,

I have queries that follow this pattern:

DESCRIBE <http://localhost> ?var
{
  SELECT ?var
  {
    ?var a ?type
  }
  OFFSET 0 LIMIT 20
}

They're used to query the contents of a page in one go -- that is,
combine the description of the page (<http://localhost> has some
metadata) with the descriptions of the "records" that are shown on it
(paginated).

This works fine over a local Model, but in a more realistic setup the
records are in a remote endpoint (while the page metadata is still in
the local Model). So I tried to turn the query into a federated one
simply by adding SERVICE:

DESCRIBE <http://localhost> ?var
{
  SERVICE <http://remote/sparql>
  {
    SELECT ?var
    {
      ?var a ?type
    }
    OFFSET 0 LIMIT 20
  }
}

But this doesn't seem to work -- I can see the SELECT being executed
remotely, but the record descriptions are not in the result. On a
second thought, this makes sense, as decriptions would probably take
another remote query.

Can this be solved with one federated query or should I just split
them and do a local DESCRIBE <http://localhost> separately?

Martynas
graphity.org