Deleting triples from default graph

[Stefano Cossu]

Hello,

I have inserted this data set on a TDB-backed database, with the 
`tdb:unionDefaultGraph` option set to true:

INSERT DATA {
  GRAPH <urn:g:1> {
    <urn:s:1> <urn:p:1> <urn:o:1> .
    <urn:s:1> <urn:p:1> <urn:o:2> .
  }
}


If I query the default graph I can see the triples:

SELECT * {
  ?s ?p ?o .
}

However, if I try to delete triples from the default graph without 
naming the named graph, the triples won't go away:

DELETE {
  <urn:s:1> <urn:p:1> <urn:o:1> .
} WHERE {
  <urn:s:1> <urn:p:1> <urn:o:1> .
}

If I specify the named graph, or use a variable for it, the triple is 
deleted. However, I am using Python's RDFLib to manage the interaction 
with Fuseki and I don't have an easy way to perform an update query on a 
graph indicated by a variable.

The default Jena graph name `<urn:x-arq:UnionGraph>` won't work either.

My configuration is pretty standard:

@prefix :      <http://base/#> . 


@prefix tdb:   <http://jena.hpl.hp.com/2008/tdb#> . 

@prefix rdf:   <http://www.w3.org/1999/02/22-rdf-syntax-ns#> . 

@prefix ja:    <http://jena.hpl.hp.com/2005/11/Assembler#> . 

@prefix rdfs:  <http://www.w3.org/2000/01/rdf-schema#> . 

@prefix fuseki: <http://jena.apache.org/fuseki#> . 



:service_tdb_all  a                   fuseki:Service ; 

        rdfs:label                    "TDB dev" ;
        fuseki:dataset                :tdb_dataset_readwrite ; 

        fuseki:name                   "dev" ;
        fuseki:serviceQuery           "query" , "sparql" ; 

        fuseki:serviceReadGraphStore  "get" ; 

        fuseki:serviceReadWriteGraphStore 

                "data" ; 

        fuseki:serviceUpdate          "update" ; 

        fuseki:serviceUpload          "upload" . 



:tdb_dataset_readwrite 

        a             tdb:DatasetTDB ; 

        tdb:unionDefaultGraph true ; 

        tdb:location  "/opt/fuseki/current/run/databases/dev" .


Is there any way I can specify a union graph IRI for update?

Thanks,
Stefano