Issue type:

• ➕ Feature request

Description:

I would like to use the SERVICE clause to perform a kind of "user-driven link traversal" (since Comunica can deal with simple RDF resources in the SERVICE clause, not just SPARQL endpoints).

This would look like that:

PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT *
WHERE {
  ?person a foaf:Person; rdfs:seeAlso ?sa.
  
  SERVICE ?sa {
    ?person foaf:knows ?other.
  }
}
LIMIT 10

Unfortunately, currently Comunica does not accept a variable after the SERVICE keyword. I wish it did...