Hi there,
For my understanding here:
Is there a reason not to have a single TDB2 dataset with several graphs
in it with "union graph" set?
On 16/01/2019 09:25, Svensson, Lars wrote:
Greetings,
I have several TDB2 datasets that I want to expose as named graphs and as a
joint dataset.
My basic idea is to have each TDB2 dataset as its own graph and then a joint
dataset combining all graphs with the default graph being the union of all
named graphs. My configuration is:
You won't get the union that way because union is a feature of the
storage.
A union is formed by
<urn:x-arq:UnionGraph> and API call DatasetGraph.getUnionGraph() work on
any dataset,
You can use in the query:
FROM <urn:x-arq:UnionGraph>
or GRAPH <urn:x-arq:UnionGraph>
and you can build a general (i.e. ad hoc graph combination) dataset with
a union graph as default graph.
More below.
@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 tdb2: <http://jena.hpl.hp.com/2016/tdb#> .
@prefix ja: <http://jena.hpl.hp.com/2005/11/Assembler#> .
@prefix : <#> .
<#service1> rdf:type fuseki:Service ;
fuseki:name "/dnb" ; # http://host:port/dnb
fuseki:serviceQuery "query" ; # SPARQL query service
fuseki:serviceReadGraphStore "data" ; # SPARQL Graph store protocol
(read only)
fuseki:dataset <#dnb> ;
.
<#dnb> a ja:RDFDataset ;
tdb2:unionDefaultGraph true ;
No effect. This is a ja:RDFDataset, not tdb2:DatasetTDB2.
tdb2:unionDefaultGraph only applies to tdb2:DatasetTDB2.
---- Example / works for me:
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 tdb2: <http://jena.apache.org/2016/tdb#>
PREFIX ja: <http://jena.hpl.hp.com/2005/11/Assembler#>
<#service_tdb> rdf:type fuseki:Service ;
rdfs:label "Selection of TDB2 graphs" ;
fuseki:name "ds" ;
fuseki:serviceQuery "query" ;
fuseki:serviceQuery "sparql" ;
fuseki:serviceUpdate "update" ;
fuseki:serviceUpload "upload" ;
fuseki:serviceReadWriteGraphStore "data" ;
# A separate read-only graph store endpoint:
fuseki:serviceReadGraphStore "get" ;
fuseki:dataset <#dataset> ;
.
# Dataset with default graph the union graph from the storage TDB2 and 2
named graphs.
<#dataset> rdf:type ja:RDFDataset ;
ja:defaultGraph <#graph> ;
ja:namedGraph [
ja:graphName <https://example/ng1> ;
ja:graph <#graph2>
];
ja:namedGraph [
ja:graphName <https://example/ng2> ;
ja:graph <#graph3>
];
.
## Graphs out of DB2.
<#graph> rdf:type tdb2:GraphTDB2 ;
tdb2:graphName "urn:x-arq:UnionGraph" ;
tdb2:location "DB2" ;
.
<#graph2> rdf:type tdb2:GraphTDB2 ;
tdb2:graphName "https://example/ng1"; ;
tdb2:location "DB2" ;
.
<#graph3> rdf:type tdb2:GraphTDB2 ;
tdb2:graphName "https://example/ng"; ;
tdb2:location "DB2" ;
.
ja:namedGraph [
ja:graphName <https://d-nb.info/datasets/authorities#dataset> ;
ja:graph <#authorities>
];
ja:namedGraph [
ja:graphName <https://d-nb.info/datasets/bib#dataset> ;
ja:graph <#bib>
];
ja:namedGraph [
ja:graphName <https://d-nb.info/datasets/dnb-all#dataset> ;
ja:graph <#dnb-all>
];
ja:namedGraph [
ja:graphName <https://d-nb.info/datasets/zdb#dataset> ;
ja:graph <#zdb>
];
.
<#authorities> a tdb2:GraphTDB ;
tdb2:GraphTDB2
tdb2:dataset <#dataset-authorities> .
tdb2:location works here but I also checked with:
## Graphs out of DB2.
<#graph> rdf:type tdb2:GraphTDB2 ;
tdb2:graphName "urn:x-arq:UnionGraph" ;
tdb2:dataset <#DB2> ;
.
<#graph2> rdf:type tdb2:GraphTDB2 ;
tdb2:graphName "https://example/ng1"; ;
tdb2:dataset <#DB2> ;
.
<#graph3> rdf:type tdb2:GraphTDB2 ;
tdb2:graphName "https://example/ng"; ;
tdb2:dataset <#DB2> ;
.
<#DB2> rdf:type tdb2:DatasetTDB2 ;
tdb2:location "DB2" ;
.
<#bib> a tdb2:GraphTDB ;
tdb2:dataset <#dataset-bib> .
<#dnb-all> a tdb2:GraphTDB ;
tdb2:dataset <#dataset-dnb-all> .
<#zdb> a tdb2:GraphTDB ;
tdb2:dataset <#dataset-zdb> .
<#dataset-authorites> a tdb2:DatasetTDB ;
tdb2:location "/home/svensson/fuseki-data/dnb/authorities/" .
<#dataset-bib> a tdb2:DatasetTDB ;
tdb2:location "/home/svensson/fuseki-data/dnb/bib/" .
<#dataset-dnb-all> a tdb2:DatasetTDB ;
tdb2:location "/home/svensson/fuseki-data/dnb/dnb-all/" .
<#dataset-zdb> a tdb2:DatasetTDB ;
tdb2:location "/home/svensson/fuseki-data/dnb/zdb/" .
When I start Fuseki, I get the following error message:
[2019-01-15 11:14:13] Server ERROR Exception in initialization: the root
file:///home/svensson/apache-jena-fuseki-3.10.0/run/configuration/service1.ttl#authorities
has no most specific type that is a subclass of ja:Object
[2019-01-15 11:14:13] WebAppContext WARN Failed startup of context
o.e.j.w.WebAppContext@46044faa{Apache Jena Fuseki
Server,/,file:///home/svensson/apache-jena-fuseki-3.10.0/webapp/,UNAVAILABLE}
org.apache.jena.assembler.exceptions.NoSpecificTypeException: the root
file:///home/svensson/apache-jena-fuseki-3.10.0/run/configuration/service1.ttl#authorities
has no most specific type that is a subclass of ja:Object
doing:
root:
file:///home/svensson/apache-jena-fuseki-3.10.0/run/configuration/service1.ttl#dnb
with type: http://jena.hpl.hp.com/2005/11/Assembler#RDFDataset assembler
class: class org.apache.jena.sparql.core.assembler.DatasetAssembler
Have I missed something obvious?
Thanks in advance,
Lars
