On 28/03/13 13:14, Milorad Tosic wrote:
Hi,
The SPARQL standard states that multiple FROM clauses in a single
> SPARQL query should be interpreted as a graph merge operation. But, I
> get strange behavior in this case not as specified. At the end of the
> message I first include results of a illustrative example that
> indicates that graphs are not merged followed byJava code for
> the same example.
> What I am doing wrong? What should be done to make the graph merge
> working? We use jena-2.6.4 and tdb-0.8.9.
Old versions, pre-Apache. It seems to work for me in current TDB.
A simple test case of your setup is one data file, one query.
== D.trig
@base <http://example/> .
<g1> { <s> <p> <x> }
<g2> { <x> <q> <o> }
== Q.rq
BASE <http://example/>
SELECT *
FROM <g1>
FROM <g2>
{
?s <p> ?x .
?x <q> <o>
}
==
tdbquery --mem D.trig --file Q.rq
==>
-------------
| s | x |
=============
| <s> | <x> |
-------------
(I also did the same with your data, converted, successfully but it's a
bit wide for email)
This is with current TDB 0.10.0 which supports --mem for quick,
in-memory testing. It creates and loads a TDB database using a RAM disk
- otherwise TDB query execution is the same as disk.
Otherwise: You will need
rm -rf DBX
tdbloader --loc=DBX D.trig
tdbquery --loc=DBX --file Q.rq
Andy
(I haven't checked the java code is working correctly)
Thanks,
Milorad
===================================================================
START
Deleting directory: C:/DatasetGraphsMergeTest
creating directory: C:/DatasetGraphsMergeTest
DIR created
WARN [main] (SetupTDB.java:755) - No BGP optimizer
First graph created.
--------------------------------------------------------------------------------------------------------------------------
| s | p | o
|
==========================================================================================================================
| <http://test/r1> | <http://www.w3.org/2000/01/rdf-schema#subPropertyOf> |
<http://www.w3.org/2000/01/rdf-schema#label> |
--------------------------------------------------------------------------------------------------------------------------
Second graph created.
----------------------------------------------------------------------------------------------
| s | p | o
|
==============================================================================================
| <http://test/r2> | <http://www.w3.org/2000/01/rdf-schema#subPropertyOf> |
<http://test/r1> |
----------------------------------------------------------------------------------------------
Inter graph query results.
---------
| s | l |
=========
---------
END
===================================================================
import java.io.File;
import java.io.IOException;
import org.apache.commons.io.FileUtils;
import com.hp.hpl.jena.query.Query;
import com.hp.hpl.jena.query.Dataset;
import com.hp.hpl.jena.query.QueryExecution;
import com.hp.hpl.jena.query.QueryExecutionFactory;
import com.hp.hpl.jena.query.QueryFactory;
import com.hp.hpl.jena.query.ResultSet;
import com.hp.hpl.jena.query.ResultSetFormatter;
import com.hp.hpl.jena.shared.Lock;
import com.hp.hpl.jena.tdb.TDB;
import com.hp.hpl.jena.tdb.TDBFactory;
import com.hp.hpl.jena.update.UpdateAction;
import com.hp.hpl.jena.update.UpdateFactory;
import com.hp.hpl.jena.update.UpdateRequest;
public class DatasetGraphsMergeSPARQL {
public static final String TDB_DIR = "C:/DatasetGraphsMergeTest";//path on
locval HDD for TDB store
public static final boolean DELETE_EXISTING_TDB = true;//if TDB already
exist should we delete it
public static final String Q_CreateGraph1 =
"INSERT DATA { " +
" GRAPH <http://g1> { " +
" <http://test/r1> <http://www.w3.org/2000/01/rdf-schema#subPropertyOf>
" +
" <http://www.w3.org/2000/01/rdf-schema#label> . " +
" }" +
"}";
public static final String Q_CreateGraph2 =
"INSERT DATA { " +
" GRAPH <http://g2> { " +
" <http://test/r2> <http://www.w3.org/2000/01/rdf-schema#subPropertyOf>
" +
" <http://test/r1> . " +
" }" +
"}";
public static final String Q_TestEmpty1 =
"SELECT ?s ?p ?o " +
"FROM <http://g1> " +
"{ " +
" ?s ?p ?o . " +
"}";
public static final String Q_TestEmpty2 =
"SELECT ?s ?p ?o " +
"FROM <http://g2> " +
"{ " +
" ?s ?p ?o . " +
"}";
public static final String Q_TestInterGraphPath =
"SELECT ?s ?l " +
"FROM <http://g1> " +
"FROM <http://g2> " +
"{ " +
" ?s <http://www.w3.org/2000/01/rdf-schema#subPropertyOf> ?l . " +
" ?l <http://www.w3.org/2000/01/rdf-schema#subPropertyOf> " +
" <http://www.w3.org/2000/01/rdf-schema#label> . " +
"}";
public static void main(String[] args) throws Exception{
Dataset m_dataset;
System.out.println("START");
m_dataset = initDataset();
updateDataset(m_dataset, Q_CreateGraph1);
System.out.println("First graph created.");
selectDataset(m_dataset, Q_TestEmpty1);
updateDataset(m_dataset, Q_CreateGraph2);
System.out.println("Second graph created.");
selectDataset(m_dataset, Q_TestEmpty2);
System.out.println("Inter graph query results.");
selectDataset(m_dataset, Q_TestInterGraphPath);
System.out.println("END");
}
public static Dataset initDataset() throws IOException{
//Initializing Dataset//Creating Directory for TDB
File tdbDir = new File(TDB_DIR);
if(DELETE_EXISTING_TDB && tdbDir.exists()){
System.out.println("Deleting directory: " + TDB_DIR);
FileUtils.deleteDirectory(tdbDir);
}
if (!tdbDir.exists()){
System.out.println("creating directory: " + TDB_DIR);
boolean result = tdbDir.mkdir();
if(result){
System.out.println("DIR created");
}
}
//Initializing Dataset
return TDBFactory.createDataset(tdbDir.getPath());
}
public static void updateDataset(Dataset dataset, String querystr){
dataset.getLock().enterCriticalSection(Lock.WRITE);
try {
UpdateRequest updateRequest = UpdateFactory.create(querystr);
UpdateAction.execute(updateRequest, dataset);
}catch (Exception e){
System.out.println(e);
} finally {
TDB.sync(dataset);
dataset.getLock().leaveCriticalSection();
}
}
public static void selectDataset(Dataset dataset, String querystr){
//SPARQL QUERY is handled here
Query query = QueryFactory.create(querystr);
dataset.getLock().enterCriticalSection(Lock.READ) ;
try {
QueryExecution qexec = QueryExecutionFactory.create(query,
dataset) ;
ResultSet results = qexec.execSelect() ;
ResultSetFormatter.out(System.out, results);
qexec.close();
} finally {
dataset.getLock().leaveCriticalSection();
}
}
}
