I am getting an empty result set when I try to retrieve the data stored in a jena model.
This is the code to load the data (I have removed the imports for brevity)
package basic;
//imports here
public class DataLoaderQn {
public static void main(String[] args) throws FileNotFoundException {
String resourceURI = "http://www.abc123.com/riskmodelling/static/risks";
String directory = "D:/mywork/dp/projs/static-risks/data/test";
Dataset dataset = TDBFactory.createDataset(directory);
Model model = null;
try {
dataset.begin(ReadWrite.WRITE);
model = dataset.getDefaultModel();
model.enterCriticalSection(Lock.WRITE);
model = model.removeAll();
Resource projectNatureRes = model.createResource(resourceURI+":PROJECT_NATURE");
Property projectNatureRiskProps = model.createProperty(resourceURI + ":COMPLEX_FUNCTIONALITY");
Bag projectNatureRisks = model.createBag();
projectNatureRisks.add("More defects");
projectNatureRisks.add("Effort estimation inaccurate");
projectNatureRes.addProperty(projectNatureRiskProps, projectNatureRisks);
Property migrationRiskProps = model.createProperty(resourceURI + ":MIGRATION");
Bag migrationRisks = model.createBag();
migrationRisks.add("Lack of knowledge of exsting application");
migrationRisks.add("Documentation not available");
projectNatureRes.addProperty(migrationRiskProps, migrationRisks);
model.write(System.out);
model.write(new FileOutputStream(new File(directory + "/Project_risk.ttl")), "N-TRIPLES");
model.commit();
dataset.commit();
TDB.sync(model);
} finally {
dataset.end();
model.leaveCriticalSection();
}
}
}
And this is how I read in the data from a java program
public class ReadBasicQn {
public static void main(String[] args) {
String directory = "D:/mywork/dp/projs/static-risks/data/test";
Dataset dataset = TDBFactory.createDataset(directory);
Model model = null;
ResultSet rs;
QueryExecution qexeExecution = null;
try{
/*model = ModelFactory.createDefaultModel();
TDBLoader.loadModel(model, directory + "/Project_risk.ttl");*/
model = dataset.getDefaultModel();
String queryString = "PREFIX proj: <http://www.abc123.com/riskmodelling/static/risks#> ";
queryString += "select ?risks where ";
queryString += "{proj:PROJECT_NATURE proj:COMPLEX_FUNCTIONALITY ?risks}";
String queryString2 = "SELECT * WHERE { ?s ?p ?o }";
Query q = QueryFactory.create(queryString);
qexeExecution = QueryExecutionFactory.create(q, model);
rs = qexeExecution.execSelect();
ResultSetFormatter.out(System.out, rs);
qexeExecution.close();
q = QueryFactory.create(queryString2);
qexeExecution = QueryExecutionFactory.create(q, model);
rs = qexeExecution.execSelect();
ResultSetFormatter.out(System.out, rs);
/*while(rs.hasNext()){
QuerySolution qSol = rs.nextSolution();
RDFNode n = qSol.get("risks");
System.out.println(n);
}*/
}finally{
qexeExecution.close();
}
}
}
The output of the second query (select *) from the ResultSetFormatter shows
------------------------------------------------------------------------------------------------------------------------------------------------
| s | p | o |
===================================================================================================================================================================================================
| <http://www.abc123.com/riskmodelling/static/risks:PROJECT_NATURE> | <http://www.abc123.com/riskmodelling/static/risks:COMPLEX_FUNCTIONALITY> | _:b0 |
| <http://www.abc123.com/riskmodelling/static/risks:PROJECT_NATURE> | <http://www.abc123.com/riskmodelling/static/risks:MIGRATION> | _:b1 |
| _:b0 | <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> | <http://www.w3.org/1999/02/22-rdf-syntax-ns#Bag> |
| _:b0 | <http://www.w3.org/1999/02/22-rdf-syntax-ns#_1> | "More defects" |
| _:b0 | <http://www.w3.org/1999/02/22-rdf-syntax-ns#_2> | "Effort estimation inaccurate" |
| _:b1 | <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> | <http://www.w3.org/1999/02/22-rdf-syntax-ns#Bag> |
| _:b1 | <http://www.w3.org/1999/02/22-rdf-syntax-ns#_1> | "Lack of knowledge of exsting application" |
| _:b1 | <http://www.w3.org/1999/02/22-rdf-syntax-ns#_2> | "Documentation not available" |
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
which means data is available and correctly loaded (correct ?). The custom query however returns the following output.
---------
| risks |
=========
---------
Any help is appreciated. I have just about started with Jena, so maybe I am doing something really foolish.
There's a typo. Your prefix ends in #, but in your URIs, there's a :. Here's your prefix declaration and URI, lined up:
prefix proj: http://www.abc123.com/riskmodelling/static/risks#>
http://www.abc123.com/riskmodelling/static/risks:PROJECT_NATURE
^
|
In your URI, it's risks[COLON]PROJECT_NATURE, not risks[HASH]PROJECT_NATURE. You need to change your prefix to:
prefix proj: http://www.abc123.com/riskmodelling/static/risks:>
or change your data to
Resource projectNatureRes = model.createResource(resourceURI+"#PROJECT_NATURE");
// ...and in a few other places, too