Re: Implicit default-graph-uri

[Andy Seaborne]

On 16/11/2023 11:35, Laura Morales wrote:
I would like to configure Fuseki such that I can use 2 datasets from 2 
different locations, as if they were a single dataset.
This is my config.ttl:


<#> a fuseki:Service ;

     fuseki:endpoint [
         fuseki:operation fuseki:query
     ] ;

     fuseki:dataset [
         a ja:RDFDataset ;

         ja:namedGraph [
             ja:graphName :graph1 ;
             ja:graph [
                 a tdb2:GraphTDB ;
                 tdb2:location "location-1" ;
             ]
         ] ;

         ja:namedGraph [
             ja:graphName :graph2 ;
             ja:graph [
                 a tdb2:GraphTDB ;
                 tdb2:location "location-2" ;
             ]
         ] ;
     ] .


There is no particular reason why I used this configuration; I mostly copied it 
from the Fuseki documentation. If it can be simplified, please suggest how.

I query Fuseki with "/service/query/?default-graph-uri=urn:x-arq:UnionGraph". I also know that I can use 
"SELECT FROM <urn:x-arq:UnionGraph>". But I would like to know if I can configure this behavior as 
the default in the main configuration file, such that I can avoid using "x-arq:UnionGraph" entirely.
Both datasets are TDB2 and contain triples only in the default unnamed graph 
(in other words do not contain any named graph inside).

I can't find a way to do that.

tdb2:unionDefaultGraph applies to a single datasets and you have two 
datasets.

Using
  ja:defaultGraph [
        a ja:Model;
        ja:subModel ...
        ja:subModel ...
    ] ;

falls foul of transaction coordination across two different models (even 
if they are views of the same database).

I though that would work - there is some attempt to extend transactions 
into graph but this seems to be pushing things too far.

    Andy