part of ontologyi have an owl file and i want to query it in jena. i used of URL of my ontology and i want to use of object properties from my ontology for query. but give me nothing output.do i need to make html document from my ontology to can query it in jena?
// Create a new query
String queryString =
"PREFIX owl: <http://www.w3.org/2002/07/owl#>"+
"PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>"+
"PREFIX base: <http://www.owl-ontologies.com/RailwaysSemantic.owl#>"+
"PREFIX dp_ontology: <http://www.semanticweb.org/ameneh/ontologies/2020/1/dp_ontology#>"+
"PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#> "+
"SELECT ?design_patterns ?createObject WHERE{ " +
"?design_patterns dp_ontology:concerned ?createObject. "+"}";
Query query = QueryFactory.create(queryString);
// Execute the query and obtain results
QueryExecution qe = QueryExecutionFactory.create(query, m);
try {
ResultSet results = qe.execSelect();
while (results.hasNext()) {
ResultSetFormatter.out(System.out, results, query);
}
}finally {
qe.close();
Related
Below SPARQL execdescribe query giving me only two prefixes as output while running with Jena query but when I run this query on virtuoso SPARQL endpoint it's giving perfect output.
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX db: <http://dbpedia.org/ontology/>
PREFIX prop: <http://dbpedia.org/property/>
DESCRIBE ?movie ?author ?genre
WHERE {
?movie rdf:type db:Film ;
prop:author ?author ;
prop:genre ?genre .
}
LIMIT 2
OFFSET 0
When I run with Jena I am getting only two line output like this,
#prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
#prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
Below is my code which I am using but with some query its working fine,
String queryString = "PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>" +
"PREFIX db: <http://dbpedia.org/ontology/> " +
"PREFIX prop: <http://dbpedia.org/property/>" +
"DESCRIBE ?movie ?author ?genre" +
"WHERE { " +
"?movie rdf:type db:Film ;" +
"prop:author ?author ;" +
"prop:genre ?genre ." +
"}" +
"LIMIT 2" +
"OFFSET 0";
QueryExecution qexec = QueryExecutionFactory.sparqlService("http://localhost:8890/sparql", queryString);
Model results = qexec.execDescribe();
results.write(System.out,"TTL");
Its perfectly giving me output on virtuoso SPARQL end point.
below is screen shot,
As suggested in comments by #AKSW, There is a space issue in the query. So after edited my query, it will perfectly work fine.
I'm tring to find informations about a place (ex : New York http://dbpedia.org/page/New_York). I' try to get informations suchs as nearestCity , museum)...
My request returns nothing...
String name = "New_York";
String s4 = "PREFIX g: <http://www.w3.org/2003/01/geo/wgs84_pos#>\n" +
"PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>\n" +
"PREFIX onto: <http://dbpedia.org/ontology/>\n" +
"PREFIX dbpedia: <http://dbpedia.org/resource/>PREFIX dcterms: <http://purl.org/dc/terms/>\n"+
"PREFIX dp: <http://dbpedia.org/resource/>\n"+
"PREFIX dbprop: <http://dbpedia.org/property/>\n" +
"PREFIX grs: <http://www.georss.org/georss/>\n"+
"PREFIX dbpedia-oll: <http://dbpedia.org/ontology/> \n"+
"PREFIX dbpedia-owl: <http://dbpedia.org/ontology/>PREFIX category: <http://dbpedia.org/resource/Category:>\n"+
"\n" +
"SELECT ?nearestCity \n" +
"WHERE\n" +
"{ OPTIONAL{onto:"+name+" grs:nearestCity ?nearestCity .}\n"+
" }\n" +
"LIMIT 300\n" +
"";
There are a couple problems with the query you are doing:
1) Some namespaces are wrong: the resource New_York has the URI: http://dbpedia.org/resource/New_York. In your query that would translate to "dbpedia:"+name instead of "onto:"+name.
2) The properties that you are looking for point to the resource New_York, not the other way around. For example, for the nearest city one, this is the query that works (note the namespaces again for the property):
SELECT ?nearestCity where {
?nearestCity <http://dbpedia.org/property/nearestCity> <http://dbpedia.org/resource/New_York>.
}LIMIT 300
(See results)
And for museum:
SELECT ?m where {
?m <http://dbpedia.org/ontology/museum> <http://dbpedia.org/resource/New_York>.
}LIMIT 300
(See results)
I am using the Jena Java framework for querying DBpedia end point using SPARQL, to get the type for all points of interest in German cities. I am facing no issue for places that have English DBpedia entries. But, when it comes to place names to be queried from the German DBpedia endpoint (http://de.dbpedia.org/resource/Schloß_Nymphenburg), this query returns no result. This problem is also mentioned over here (http://mail-archives.apache.org/mod_mbox/jena-users/201110.mbox/%3C4E877C8A.4050705#apache.org%3E). Even after referring to this, I am unable to solve the problem. I don't know how to work with QueryEngineHTTP. I am adding two code snippets - one that works (first one - query for Allianz Arena : which has an English entry in DBpedia) and one that doesn't work (second one - for Schloß Nymphenburg, that has a German entry).
This might be a very trivial issue, but I am unable to solve it. Any pointers to a solution would be very very helpful.
Thanks a lot!
Code 1 - working :
String service = "http://dbpedia.org/sparql";
final ParameterizedSparqlString query = new ParameterizedSparqlString(
"PREFIX geo: <http://www.w3.org/2003/01/geo/wgs84_pos#>" +
"PREFIX dbo: <http://dbpedia.org/ontology/>" +
"PREFIX dcterms: <http://purl.org/dc/terms/>" +
"SELECT * WHERE {" +
"?s geo:lat ?lat ." +
"?s geo:long ?long ." +
"?s dcterms:subject ?sub}");
query.setIri("?s", "http://dbpedia.org/resource/Allianz_Arena");
QueryExecution qe = QueryExecutionFactory.sparqlService(service, query.toString());
ResultSet results = qe.execSelect();
ResultSetFormatter.out(System.out, results);
Code 2 - not working :
String service = "http://dbpedia.org/sparql";
final ParameterizedSparqlString query = new ParameterizedSparqlString(
"PREFIX geo: <http://www.w3.org/2003/01/geo/wgs84_pos#>" +
"PREFIX dbo: <http://dbpedia.org/ontology/>" +
"PREFIX dcterms: <http://purl.org/dc/terms/>" +
"SELECT * WHERE {" +
"?s geo:lat ?lat ." +
"?s geo:long ?long ." +
"?s dcterms:subject ?sub}");
query.setIri("?s", "http://de.dbpedia.org/resource/Schloß_Nymphenburg");
QueryExecution qe = QueryExecutionFactory.sparqlService(service, query.toString());
ResultSet results = qe.execSelect();
ResultSetFormatter.out(System.out, results);
I don't think this is an issue with jena at all. Trying:
SELECT * WHERE {
<http://de.dbpedia.org/resource/Schloß_Nymphenburg> ?p ?o }
at http://dbpedia.org/sparql I get no results: try it yourself.
SELECT * WHERE {
<http://de.dbpedia.org/resource/Schloss_Nymphenburg> ?p ?o }
by contrast returns something, even if it's just a bunch of cross links.
I'm trying to create a SPARQL query with Jena to query DBpedia. The query is working when I use Virtuoso but when I plug it into the following Java code, it returns an empty set.
String sr="Christopher_Nolan";
String sparqlQueryString1 = "PREFIX dbont: <http://dbpedia.org/ontology/> "+
"PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>"+
"PREFIX foaf: <http://xmlns.com/foaf/0.1/> "+
" SELECT distinct ?s"+
" WHERE { "+
"?s foaf:name ?label ." +
"filter(?label=\"Christpher_Nolan\"#en)." +
" }";
Query query = QueryFactory.create(sparqlQueryString1);
QueryExecution qexec = QueryExecutionFactory.sparqlService("http://dbpedia.org/sparql", query);
ResultSet results = qexec.execSelect();
ResultSetFormatter.out(System.out,results, query);
qexec.close() ;
I don't think this is a problem with Jena, but with your particular query. Your query, when run on the DBpedia SPARQL endpoint, produces no results
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT distinct ?s
WHERE {
?s foaf:name ?label .
filter(?label="Christpher_Nolan"#en)
}
SPARQL results (no results)
However, if you add an o to the name Christopher, and change the underscore to a space, you get three results:
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT distinct ?s
WHERE {
?s foaf:name ?label .
filter(?label="Christopher Nolan"#en)
}
SPARQL results (3 results)
s
http://dbpedia.org/resource/Christopher_Nolan_(author)
http://dbpedia.org/resource/Christopher_Nolan
http://dbpedia.org/resource/Chris_Nolan_(musician)
I'd also point out that this is a rather unusual use of filter. If you want to select triples that use a certain value, just put that value into the triple pattern:
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT distinct ?s
WHERE {
?s foaf:name "Christopher Nolan"#en
}
SPARQL results (same 3 results)
I am trying to extract labels from DBpedia for some persons. I am partially successful now, but I got stuck in the following problem. The following code works.
public class DbPediaQueryExtractor {
public static void main(String [] args) {
String entity = "Aharon_Barak";
String queryString ="PREFIX dbres: <http://dbpedia.org/resource/> SELECT * WHERE {dbres:"+ entity+ "<http://www.w3.org/2000/01/rdf-schema#label> ?o FILTER (langMatches(lang(?o),\"en\"))}";
//String queryString="select * where { ?instance <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://xmlns.com/foaf/0.1/Person>; <http://www.w3.org/2000/01/rdf-schema#label> ?o FILTER (langMatches(lang(?o),\"en\")) } LIMIT 5000000";
QueryExecution qexec = getResult(queryString);
try {
ResultSet results = qexec.execSelect();
for ( ; results.hasNext(); )
{
QuerySolution soln = results.nextSolution();
System.out.print(soln.get("?o") + "\n");
}
}
finally {
qexec.close();
}
}
public static QueryExecution getResult(String queryString){
Query query = QueryFactory.create(queryString);
//VirtuosoQueryExecution vqe = VirtuosoQueryExecutionFactory.create (sparql, graph);
QueryExecution qexec = QueryExecutionFactory.sparqlService("http://dbpedia.org/sparql", query);
return qexec;
}
}
However, when the entity contains brackets, it does not work. For example,
String entity = "William_H._Miller_(writer)";
leads to this exception:
Exception in thread "main" com.hp.hpl.jena.query.QueryParseException: Encountered " "(" "( "" at line 1, column 86.`
What is the problem?
It took some copying and pasting to see what exactly was going on. I'd suggest that you put newlines in your query for easier readability. The query you're using is:
PREFIX dbres: <http://dbpedia.org/resource/>
SELECT * WHERE
{
dbres:??? <http://www.w3.org/2000/01/rdf-schema#label> ?o
FILTER (langMatches(lang(?o),"en"))
}
where ??? is being replaced by the contents of the string entity. You're doing absolutely no input validation here to ensure that the value of entity will be legal to paste in. Based on your question, it sounds like entity contains William_H._Miller_(writer), so you're getting the query:
PREFIX dbres: <http://dbpedia.org/resource/>
SELECT * WHERE
{
dbres:William_H._Miller_(writer) <http://www.w3.org/2000/01/rdf-schema#label> ?o
FILTER (langMatches(lang(?o),"en"))
}
You can paste that into the public DBpedia endpoint, and you'll get a similar parse error message:
Virtuoso 37000 Error SP030: SPARQL compiler, line 6: syntax error at 'writer' before ')'
SPARQL query:
define sql:big-data-const 0
#output-format:text/html
define sql:signal-void-variables 1 define input:default-graph-uri <http://dbpedia.org> PREFIX dbres: <http://dbpedia.org/resource/>
SELECT * WHERE
{
dbres:William_H._Miller_(writer) <http://www.w3.org/2000/01/rdf-schema#label> ?o
FILTER (langMatches(lang(?o),"en"))
}
Better than hitting DBpedia's endpoint with bad queries, you can also use the SPARQL query validator, which reports for that query:
Syntax error: Lexical error at line 4, column 34. Encountered: ")" (41), after : "writer"
In Jena, you can use the ParameterizedSparqlString to avoid these sorts of issues. Here's your example, reworked to use a parameterized string:
import com.hp.hpl.jena.query.ParameterizedSparqlString;
public class PSSExample {
public static void main( String[] args ) {
// Create a parameterized SPARQL string for the particular query, and add the
// dbres prefix to it, for later use.
final ParameterizedSparqlString queryString = new ParameterizedSparqlString(
"PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>\n" +
"SELECT * WHERE\n" +
"{\n" +
" ?entity rdfs:label ?o\n" +
" FILTER (langMatches(lang(?o),\"en\"))\n" +
"}\n"
) {{
setNsPrefix( "dbres", "http://dbpedia.org/resource/" );
}};
// Entity is the same.
final String entity = "William_H._Miller_(writer)";
// Now retrieve the URI for dbres, concatentate it with entity, and use
// it as the value of ?entity in the query.
queryString.setIri( "?entity", queryString.getNsPrefixURI( "dbres" )+entity );
// Show the query.
System.out.println( queryString.toString() );
}
}
The output is:
PREFIX dbres: <http://dbpedia.org/resource/>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
SELECT * WHERE
{
<http://dbpedia.org/resource/William_H._Miller_(writer)> rdfs:label ?o
FILTER (langMatches(lang(?o),"en"))
}
You can run this query at the public endpoint and get the expected results. Notice that if you use an entity that doesn't need special escaping, e.g.,
final String entity = "George_Washington";
then the query output will use the prefixed form:
PREFIX dbres: <http://dbpedia.org/resource/>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
SELECT * WHERE
{
dbres:George_Washington rdfs:label ?o
FILTER (langMatches(lang(?o),"en"))
}
This is very convenient, because you don't have to do any checking about whether your suffix, i.e., entity, has any characters that need to be escaped; Jena takes care of that for you.