Ok.
I want to host a SPARQL end point which serves up data from a couple of
different systems, which I will load into an SDB data store. These are APNI
(Australian Pant Names Index) and AFD (Australian Faunal Directory). Ideally, I
would like people to be able to query against either graph, and also the union
of the graphs.
I am attempting to get a minimal JOSEKI server up, using SDB and named graphs.
My SDB database has two quadruples in it:
=============================================================
http://test.org/A, http://test.org/A#A, http://test.org/voc#name, "My
name is A"
http://test.org/B, http://test.org/B#B, http://test.org/voc#name, "My
name is B"
=============================================================
This is my joseki config:
=============================================================
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
@prefix module: <http://joseki.org/2003/06/module#> .
@prefix joseki: <http://joseki.org/2005/06/configuration#> .
@prefix ja: <http://jena.hpl.hp.com/2005/11/Assembler#> .
@prefix sdb: <http://jena.hpl.hp.com/2007/sdb#> .
<> rdfs:label "Joseki Configuration File - SDB example" .
[]
rdf:type joseki:Server;
joseki:serverDebug "true".
[] ja:loadClass "com.hp.hpl.jena.sdb.SDB" .
sdb:DatasetStore rdfs:subClassOf ja:RDFDataset .
sdb:Model rdfs:subClassOf ja:Model .
<#service1>
rdf:type joseki:Service ;
rdfs:label "SPARQL-SDB";
joseki:serviceRef "sparql"; # web.xml must route this name to Joseki
joseki:dataset [
rdf:type sdb:DatasetStore;
joseki:poolSize 2;
sdb:store [
rdf:type sdb:Store ;
sdb:layout "layout2/index";
sdb:connection [
rdf:type sdb:SDBConnection;
sdb:sdbType "MySQL";
sdb:sdbHost "localhost";
sdb:sdbName "jena";
sdb:sdbUser "jena";
sdb:sdbPassword "jena";
sdb:rdbType "MySQL";
sdb:driver "com.mysql.jdbc.Driver"
]
]
] ;
joseki:processor [
rdfs:label "SPARQL processor for fixed datasets" ;
rdf:type joseki:Processor ;
module:implementation [
rdf:type joseki:ServiceImpl;
module:className <java:org.joseki.processors.SPARQL>
] ;
joseki:allowExplicitDataset "false"^^xsd:boolean ;
joseki:allowWebLoading "false"^^xsd:boolean ;
joseki:lockingPolicy joseki:lockingPolicyMRSW
];
.
=============================================================
Joseki launches ok. When I fetch this URL:
=============================================================
http://localhost:2020/sparql?query=select ?s ?p ?o where { ?s ?p ?o }
=============================================================
I get this stack trace
=============================================================
11:33:00 INFO SPARQL :: Throwable:
com.hp.hpl.jena.sparql.core.Quad.isDefaultGraphIRI()Z
java.lang.NoSuchMethodError:
com.hp.hpl.jena.sparql.core.Quad.isDefaultGraphIRI()Z
at
com.hp.hpl.jena.sdb.compiler.SqlStageBasicQuad.build(SqlStageBasicQuad.java:67)
at com.hp.hpl.jena.sdb.compiler.SqlStageList.build(SqlStageList.java:23)
… etc
=============================================================
There are several issues.
First, a NoSuchMethodError means that the runtime classpath is not the same as
the classpath with which the code was compiled. My joseki is simply the version
that I downloaded from the web -
http://sourceforge.net/projects/joseki/files/Joseki-SPARQL/Joseki-3.4.4/joseki-3.4.4.zip/download
That it gets (even can get) this error anywhere is a bit of a worry.
The next problem is that, obviously, I really don't understand the
configuration stuff. I also don't understand sparql itself well enough yet.
Ideally: i would like to have two named graphs GraphA and GraphB. I would also
like to have a named graph GraphAB. And I would like GraphAB to be the default
graph. This permits me to do versioning - I can load "data from APNI October"
into SDB, and make the default graph be "APNI October data and AFD June data
and CommonTerms"
The thing is: looking at the Joseki example config files, there's a section
that says:
# Service publishes the whole of the SDB store - this is the usual way
to use SDB.
But looking into it a bit more closely, It would seem that this is meant to
work with the anonymous triples rather than the quadruples. Ok … but why do I
get an exception? Shouldn't it just be saying "there are no triples in this
graph" because the triples table is empty?
So lets try the bit that allows you to pick one particular graph.
=============================================================
joseki:dataset [
rdf:type ja:RDFDataset ;
ja:defaultGraph [
rdf:type sdb:Model ;
sdb:graphName <http://test.org/A> ;
sdb:dataset [
rdf:type sdb:DatasetStore;
joseki:poolSize 2;
sdb:store [
rdf:type sdb:Store ;
sdb:layout "layout2/index";
sdb:connection [
rdf:type sdb:SDBConnection;
sdb:sdbType "MySQL";
sdb:sdbHost "localhost";
sdb:sdbName "jena";
sdb:sdbUser "jena";
sdb:sdbPassword "jena";
sdb:rdbType "MySQL";
sdb:driver "com.mysql.jdbc.Driver"
]
]
] ;
]
] ;
=============================================================
Nope. Same problem. A java error - quite a low-level one. All right. Lets try
an older version of Joseki.
… OMG! OMG! Success!
So, the issue appears to be that the 3.4.4 download at source forge is bad.
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