使用 sparql、java、Jena API 查询 DBPedia 本体

Question

我正在尝试使用来自javacode的sparql查询DBPedia对于某些查询，它可以完美地工作，而对于另一个查询则不起作用。我不认为我的查询中有错误，因为我已经在 DBPedia aparql 端点中对其进行了测试。这是我的java代码：

package ja1;
import com.hp.hpl.jena.query.*;
import com.hp.hpl.jena.rdf.model.*;
import com.hp.hpl.jena.util.*;
    public class Q_DBP_Online {
        public static void main(String[]args)
            {
                sparqlTest();
            }
    public static void sparqlTest()
       {             
         /*String queryString = "SELECT ?o WHERE {"+
                                "?s ?p ?o ."+
                                "} LIMIT 10";*/
         String str="Obama";
         String queryString = "PREFIX pr:<http://xmlns.com/foaf/0.1/>" +
                              "PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>"+ 
                              "SELECT DISTINCT ?s ?label WHERE {" +                                        
                              "?s rdfs:label ?label . "+
                              "?s a pr:Person."+
                              "FILTER (lang(?label) = 'en'). "+
                              "?label bif:contains"+str+" ."+
                              "}";
         Query query = QueryFactory.create(queryString);        
         QueryExecution qexec =         QueryExecutionFactory.sparqlService("http://dbpedia.org/sparql", query);
         try
          {
            ResultSet results = qexec.execSelect();
            while(results.hasNext()){
           QuerySolution soln = results.nextSolution();
           //Literal name = soln.getLiteral("x");
           System.out.println(soln);
                }
             }
         finally{
              qexec.close();
          }
    }
}

因此，第一个被注释的查询运行良好，第二个查询没有运行，我在netbeans中收到以下消息：

SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/home/rodwan/Desktop/Th_Pr/apache-jena-2.12.1/lib/slf4j-log4j12-1.7.6.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/home/rodwan/Desktop/Th_Pr/pellet-2.3.1/lib/jena/slf4j-log4j12-1.6.4.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
SLF4J: Actual binding is of type [org.slf4j.impl.Log4jLoggerFactory]
Exception in thread "main" com.hp.hpl.jena.query.QueryParseException: Encountered " "(" "( "" at line 1, column 169.
Was expecting one of:
    "values" ...
    "graph" ...
    "optional" ...
    "minus" ...
    "bind" ...
    "service" ...
    "filter" ...
    "{" ...
    "}" ...
    ";" ...
    "," ...
    "." ...
    at com.hp.hpl.jena.sparql.lang.ParserSPARQL11.perform(ParserSPARQL11.java:102)
    at com.hp.hpl.jena.sparql.lang.ParserSPARQL11.parse$(ParserSPARQL11.java:53)
    at com.hp.hpl.jena.sparql.lang.SPARQLParser.parse(SPARQLParser.java:37)
    at com.hp.hpl.jena.query.QueryFactory.parse(QueryFactory.java:148)
    at com.hp.hpl.jena.query.QueryFactory.create(QueryFactory.java:80)
    at com.hp.hpl.jena.query.QueryFactory.create(QueryFactory.java:53)
    at com.hp.hpl.jena.query.QueryFactory.create(QueryFactory.java:41)
    at ja1.Q_DBP_Online.sparqlTest(Q_DBP_Online.java:38)
    at ja1.Q_DBP_Online.main(Q_DBP_Online.java:18)
Java Result: 1
BUILD SUCCESSFUL (total time: 1 second)
----------------------------------

Answer 1

我已经尝试过你的例子，但似乎有一些遗漏的空格。以下内容在DBPedia上为我工作：

PREFIX pr:<http://xmlns.com/foaf/0.1/>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
SELECT DISTINCT ?s ?label WHERE {?s rdfs:label ?label . ?s a pr:Person . FILTER (lang(?label) = 'en') . ?label bif:contains "Obama" .}

到 Java 的翻译如下所示：

String queryString = "PREFIX pr:<http://xmlns.com/foaf/0.1/>n" +
                              "PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>n"+
                              "SELECT DISTINCT ?s ?label WHERE {" +                              "?s rdfs:label ?label . "+
                              "?s a pr:Person . "+
                              "FILTER (lang(?label) = 'en') . "+
                              "?label bif:contains ""+str+"" ."+
                              "}";

希望这有帮助。

Answer 2

问题是查询解析器会严格检查你是否都使用了在查询开头声明的前缀，而bif:contains显然不是这样——这实际上是 Virtuoso 的内置属性。

您已经提供了一个使用角牙套的解决方案，即 <bif:contains> .

另一种方法是使用类 QueryEngineHttp

QueryEngineHttp qe = new QueryEngineHttp(queryString);

并且只需将查询字符串发送到终结点，而不是将其解析为 Query 对象。