Download DBpedia locally with Jena TDB?

Question

I need to query DBpedia:

SELECT DISTINCT ?poi ?lat ?long ?photos ?template ?type ?label WHERE { ?poi <http://www.w3.org/2000/01/rdf-schema#label> ?label . ?poi <http://www.w3.org/2003/01/geo/wgs84_pos#lat> ?lat . ?poi <http://www.w3.org/2003/01/geo/wgs84_pos#long> ?long . ?poi <http://dbpedia.org/property/hasPhotoCollection> ?photos . OPTIONAL {?poi <http://dbpedia.org/property/wikiPageUsesTemplate> ?template } . OPTIONAL {?poi <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?type } . FILTER ( ?lat > x && ?lat < y && ?long > z && ?long < ω && langMatches( lang(?label), "EN" )) } 

I assume that this information is scattered among different dump files (.nt), and somehow the SPARQL endpoint serves us with a set of results. I need to download these different .nt files locally (not all DBpedia), execute my query only once and save the results locally (I don't want to use the SPARQL endpoint).

• What parts of the yen should be used for this launch?

I am a little confused by reading this post :

Thus, you can load all DBPedia data into one TDB location on disk (i.e. in one directory). This way you can run SPARQL queries over it.

• How to load DBpedia in one place in TDB in terms of Jena if we got three .nt DBpedia files? How do we apply the above request to these .nt files? (Any code will help.)

• Example, is this wrong?

  String tdbDirectory = "C:\\TDB"; String dbdump1 = "C:\\Users\\dump1_en.nt"; String dbdump2 = "C:\\Users\\dump2_en.nt"; String dbdump3 = "C:\\Users\\dump3_en.nt"; Dataset dataset = TDBFactory.createDataset(tdbDirectory); Model tdb = dataset.getDefaultModel(); //<-- What is the default model?Should I care? //Model tdb = TDBFactory.createModel(tdbdirectory) ;//<--is this prefered? FileManager.get().readModel( tdb, dbdump1, "N-TRIPLES" ); FileManager.get().readModel( tdb, dbdump2, "N-TRIPLES" ); FileManager.get().readModel( tdb, dbdump3, "N-TRIPLES" ); String q = "my big fat query"; Query query = QueryFactory.create(q); QueryExecution qexec = QueryExecutionFactory.create(query, tdb); ResultSet results = qexec.execSelect(); while (results.hasNext()) { //do something significant with it } qexec.close() tdb.close() ; dataset.close(); 

• In the above code, we used "dataset.getDefaultModel" (to get the default graph as a Jena Model ). Is this statement valid? Do we need to create a dataset to execute the query, or should we go with TDBFactory.createModel(tdbdirectory) ?

Answer 1

To localize the yen index locally:

 /** The Constant tdbDirectory. */ public static final String tdbDirectory = "C:\\TDBLoadGeoCoordinatesAndLabels"; /** The Constant dbdump0. */ public static final String dbdump0 = "C:\\Users\\Public\\Documents\\TDB\\dbpedia_3.8\\dbpedia_3.8.owl"; /** The Constant dbdump1. */ public static final String dbdump1 = "C:\\Users\\Public\\Documents\\TDB\\geo_coordinates_en\\geo_coordinates_en.nt"; ... Model tdbModel = TDBFactory.createModel(tdbDirectory);<\n> /*Incrementally read data to the Model, once per run , RAM > 6 GB*/ FileManager.get().readModel( tdbModel, dbdump0); FileManager.get().readModel( tdbModel, dbdump1, "N-TRIPLES"); FileManager.get().readModel( tdbModel, dbdump2, "N-TRIPLES"); FileManager.get().readModel( tdbModel, dbdump3, "N-TRIPLES"); FileManager.get().readModel( tdbModel, dbdump4, "N-TRIPLES"); FileManager.get().readModel( tdbModel, dbdump5, "N-TRIPLES"); FileManager.get().readModel( tdbModel, dbdump6, "N-TRIPLES"); tdbModel.close(); 

Request Jena:

 String queryStr = "dbpedia query "; Dataset dataset = TDBFactory.createDataset(tdbDirectory); Model tdb = dataset.getDefaultModel(); Query query = QueryFactory.create(queryStr); QueryExecution qexec = QueryExecutionFactory.create(query, tdb); /*Execute the Query*/ ResultSet results = qexec.execSelect(); while (results.hasNext()) { // Do something important } qexec.close(); tdb.close() ;