Help for an issue on Jena Assembler (configuration of UnionModel with GraphTDB2 as rootModel)

[an...@orange.com]

Hello,

I am requesting your help with an issue about Jena Assembler:


I have a Fuseki2 server (3.10.0) configured with a Jena Assembler config file.

The goal is to have a Dataset exposing two named graph:

-          "Model" named graph is a Memory Model that define a custom Ontology

-          "Data" named graph is a GraphTDB2 Model used to store individuals (All triples are persisted in TDB)

I am working on a way to have the default graph of this dataset to be a Union Model.
This way, the default graph would be the union of Data + Model for Selects queries, and for Update queries triples will be inserted in the Data graph under the hood,

Below the interesting part of my configuration file:


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

@prefix tdb2:     <http://jena.apache.org/2016/tdb#> .



[...]



<#dataset> a ja:RDFDataset ;

      ja:defaultGraph <#unionGraph> ;

      ja:namedGraph

            [

                  ja:graphName <uri:context/model> ;

                  ja:graph <#modelGraph>

            ] ;

      ja:namedGraph

            [

                  ja:graphName <uri:context/data> ;

                  ja:graph <#dataGraph>

            ] ;

      .







<#modelGraph> a ja:MemoryModel ;

      ja:content [ ja:externalContent <file :ontology.ttl> ] ;

      .



<#dataGraph> a tdb2:GraphTDB2 ;

      tdb2:location "tdb" ;

      .



<#unionGraph> a ja:UnionModel ;

      ja:rootModel <#dataGraph> ;

      ja:subModel <#modelGraph> ;

      .

When I start Fuseki2 server with this configuration, the server start correctly, but I have an issue when performing SPARQL requests:
From Fuseki2 Web page, any Select  requests on any of the three Graph produce a "TransactionException: Not in a transaction", and for update requests it produce a "TransactionException: Currently in an active transaction"

This error is not happening when <#unionGraph> is defined as:


<#unionGraph> a ja:UnionModel ;

      ja:subModel <#modelGraph> , <#dataGraph> ;

      .

And I have no transaction issue even when I try to perform queries on <#dataGraph> that requires Transaction to be used (I think Fuseki2 must make the transaction itself ).


But somehow, all Fuseki2 endpoints are broken (meaning incomprehensible issues with Transactions) when I try to use ja:rootModel with <#dataGraph>.
I guess the way to fix it is to tell to Jena that <#unionGraph> must use Transaction because the rootModel is a graphTDB2 individual.

So I have tried to use "ja:transactional" with <#unionGraph > as a Subject but it's not working, (I'm not sure about the use of ja:transactional) .
And I can't make my dataset to be a tdb2:DatasetTDB2 because it's ignoring  all configurations coming from ja: namespace.



Does anyone knows how to have a working UnionModel with a GraphTDB2 as rootModel ?
Is it a missing feature of Jena Assembler ? Or a bug ?

In advance, thanks for helping me with this issue.


Cordially,
Antoine.


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