java - 使用 Jena TDB 在本地加载 DBpedia？

Question

我需要对 DBpedia 执行查询:

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" ))
} 

我猜这些信息分散在不同的转储 (.nt) 文件中，并且 SPARQL 端点以某种方式为我们提供了一个结果集。我需要在本地下载这些不同的 .nt 文件(不是所有 DBpedia)，只执行一次查询并将结果存储在本地(我不想使用 SPARQL 端点)。

• 这次运行我应该使用耶拿的哪些部分？

我从 this post 读起来有点困惑:

So, you can load the entire DBPedia data into a single TDB location on disk (i.e. a single directory). This way, you can run SPARQL queries over it.

• 如果我们有三个 .nt DBpedia 文件，我如何将 DBpedia 加载到单个 TDB 位置？我们如何对这些 .nt 文件应用上述查询？ (任何代码都会有所帮助。)

• 例子，这样错了吗？

 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();

• 在上面的代码中，我们使用了 "dataset.getDefaultModel"(将默认图形作为 Jena Model)。这个声明有效吗？我们是否需要创建数据集来执行查询，还是应该使用 TDBFactory.createModel(tdbdirectory)？

Answer 1

让 Jena 在本地建立索引:

/** 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();

查询耶拿:

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() ;