On 03/10/12 20:24, Stephen Allen wrote:
All,
So I'm trying to test the streaming SPARQL Update changes I've done in
ARQ and Fuseki. I've created a class called GraphStoreNull, which
implements the GraphStore interface. It basically throws away all
quads that are added/removed and always answers with a null iterator
when querying. I want to use it for stress testing the streaming
implementation by sending in a bunch of massively large SPARQL Update
requests (which jena-client can generate and stream over HTTP).
Anyway, the stumbling block I'm running into is how to create a config
file for Fuseki to use this class as the basis for a dataset. I can't
seem to wrap my head around the whole Assembler functionality. I've
got a config that looks like this:
=====================
@prefix : <#> .
@prefix fuseki: <http://jena.apache.org/fuseki#> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix tdb: <http://jena.hpl.hp.com/2008/tdb#> .
@prefix ja: <http://jena.hpl.hp.com/2005/11/Assembler#> .
[] rdf:type fuseki:Server ;
fuseki:services (
<#service1>
) .
<#service1> rdf:type fuseki:Service ;
fuseki:name "ds" ;
fuseki:serviceQuery "sparql" ;
fuseki:serviceQuery "query" ;
fuseki:serviceUpdate "update" ;
fuseki:serviceUpload "upload" ;
fuseki:serviceReadWriteGraphStore "data" ;
fuseki:serviceReadGraphStore "get" ;
fuseki:dataset <#emptyDataset> ;
.
<#emptyDataset> rdf:type ja:RDFDataset . # this seems to make it use
an in-memory model
====================
What do I need to specify to make it use
"com.hp.hpl.jena.sparql.modify.GraphStoreNull" as the backing store
for #service1?
The internals of the assemblers are not very easy to follow. They only
get touched once in a blue moon so the knowledge is in obscure bits of
code.
You need to do the following
1/ Write an assembler for the new thing
2/ register it.
3/ Add a rdfs:subClassOf relationship
See DatasetAssembler for an example
== Write an assembler
public class DatasetNullAssembler extends AssemblerBase {
@Override
public Object open(Assembler a, Resource root, Mode mode)
{
return new GraphStoreNull()
}
}
== Register an assembler
See AssemblerUtils.registerWith
has the ARQ specific registrations.
( I have just changed the name from "register" to make it accurate :-)
== subclass
Put this in the description (it should be possible to do this in code
somewhere but I can't see where - if anyone finds out please say, it
would be good to have elsewhere as well.).
ja:DatasetNull rdfs:subClassOf ja:RDFDataset .
== Testing
I did sparql --desc desc.ttl 'SELECT * { ?s ?p ?o }' and got an empty
result.
I didn't test with Fuseki itself.
I have prodded Jenkins to do a complete developer build so it will be
propagating to Fuseki in the next hour or so.
-- desc.ttl
--------------------
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix ja: <http://jena.hpl.hp.com/2005/11/Assembler#> .
ja:DatasetNull rdfs:subClassOf ja:RDFDataset .
<#emptyDataset> rdf:type ja:DatasetNull .
--------------------
You don't need the ja:loadClass magic code to bring in custom code (as
TDB does currently) because this is built into ARQ.
[] ja:loadClass "com.hp.hpl.jena.tdb.TDB" .
tdb:DatasetTDB rdfs:subClassOf ja:RDFDataset .
tdb:GraphTDB rdfs:subClassOf ja:Model .
------------------------
Before you do this, you might like to "svn update". Having had to
remember how this works, I added what you might need at least as a
start. Having done it, I might as well commit the changes.
Andy
-Stephen
