Question

我是dotNetRDF和SPARQL的新手，我正在尝试从DBPedia中检索一些人员数据。我已经编写了这个查询并在http://dbpedia.org/sparql的在线编辑器上成功测试了它：

问题是，当我尝试使用下面的代码启动查询时，我收到HTTP异常400，无效请求：

SparqlRemoteEndpoint endpoint = new SparqlRemoteEndpoint(new Uri("http://dbpedia.org/sparql"));

        //Make a SELECT query against the Endpoint
        SparqlResultSet results = endpoint.QueryWithResultSet(@" 
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>\n
PREFIX type: <http://dbpedia.org/class/yago/>\n
PREFIX prop: <http://dbpedia.org/ontology/>\n
\n
select DISTINCT ?person ?name ?birth ?shortDescription where {\n
?person a dbpedia-owl:Person ;\n
      foaf:name ?name ;\n
      dbpedia-owl:birthDate ?birth ;\n
      dbpprop:shortDescription ?shortDescription .\n
filter langMatches(lang(?name),'en') .\n
filter langMatches(lang(?shortDescription),'en') \n
}\n
LIMIT 10");
        foreach (SparqlResult result in results)
        {
            Console.WriteLine(result.ToString());
        }

任何帮助将不胜感激。在此先感谢;）

Answer 1

这主要是因为没有正确使用c＃verbatim字符串文字。通过使用@"...，您指示c＃不解释\n之类的转义序列，但要逐字记录。同时，这也允许您编写已包含隐式\n。

的多行字符串

因此，您应该删除查询字符串中的@或\n。

另外，我建议始终将()放在filter条款旁边而不是以.结尾：

SparqlResultSet results = endpoint.QueryWithResultSet(@" 
    PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
    PREFIX type: <http://dbpedia.org/class/yago/>
    PREFIX prop: <http://dbpedia.org/ontology/>

    select DISTINCT ?person ?name ?birth ?shortDescription where {
          ?person a dbpedia-owl:Person ;
              foaf:name ?name ;
              dbpedia-owl:birthDate ?birth ;
              dbpprop:shortDescription ?shortDescription .
          filter(langMatches(lang(?name),'en'))
          filter(langMatches(lang(?shortDescription),'en'))
    }
    LIMIT 10");

Answer 2

For the XML version error you can instruct dotNetRDF to request results in a non-XML format e.g.

endpoint.ResultsAcceptHeader = "application/sparql-results+json";

Would ask for JSON instead of XML which will avoid the XML version issue.

As the documentation for that property says:

Can be used to workaround buggy endpoints which don't like the broad Accept Header that dotNetRDF sends by default

dotNetRDF查询DBPedia时出现Http错误

2 个答案: