1

我正在尝试使用dotNetRDF将以下查询发送到DBpedia：

PREFIX rdf:  <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX xsd:  <http://www.w3.org/2001/XMLSchema#>
PREFIX temp: <http://www.example.com/temp/>

CONSTRUCT {
  ?v1 a temp:r.
  ?v1 temp:p0 ?v2.
}
WHERE {
  OPTIONAL {
    {
      {
        SELECT ?v1
        WHERE {
          ?v1 rdfs:comment ?v2.
        }
        LIMIT 10
      }.
      ?v1 rdfs:comment ?v2.
    }.
  }.
}

但是，我听说发现RdfParseException了一个意外r字符（114 是 的十进制字符代码r）。

当我对同一个查询使用基于 Web 的 DBpedia SPARQL 表单时，我得到了看起来合理的结果。因此，我认为我的 SPARQL 查询没有问题，或者至少没有 DBpedia 无法处理的问题。

我试图通过启用和来遵循这个问题关于类似问题的建议。如该问题的已接受答案中所述，这确实会将收到的响应打印到 stderr。但是，它不会引起“不同的错误”；相反，查询似乎是成功的，但是返回的图是空的（它不包含三元组）。Options.HttpDebuggingOptions.HttpFullDebugging

这是重现该问题的最小示例：

using System;
using System.Runtime.ConstrainedExecution;

using VDS.RDF;
using VDS.RDF.Query;
using VDS.RDF.Writing;

namespace DotNetRdfParsingError
{
    class Program
    {
        public static void Main(string[] args)
        {
            var endpoint = new SparqlRemoteEndpoint(new Uri("http://dbpedia.org/sparql"));

            string query =
                "PREFIX rdf:  <http://www.w3.org/1999/02/22-rdf-syntax-ns#>\n" +
                "PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>\n" +
                "PREFIX xsd:  <http://www.w3.org/2001/XMLSchema#>\n" +
                "PREFIX temp: <http://www.example.com/temp/>\n" +
                "\n" +
                "CONSTRUCT {\n" +
                "  ?v1 a temp:r.\n" +
                "  ?v1 temp:p0 ?v2.\n" +
                "}\n" +
                "WHERE {\n" +
                "  OPTIONAL {\n" +
                "    {\n" +
                "      {\n" +
                "        SELECT ?v1\n" +
                "        WHERE {\n" +
                "          ?v1 rdfs:comment ?v2.\n" +
                "        }\n" +
                "        LIMIT 10\n" +
                "      }.\n" +
                "      ?v1 rdfs:comment ?v2.\n" +
                "    }.\n" +
                "  }.\n" +
                "}";

            Console.WriteLine("Without HTTP debugging:");
            try {
                var graph = endpoint.QueryWithResultGraph(query);
                PrintGraph(graph);
            }
            catch (Exception ex) {
                Console.WriteLine("EXCEPTION:\n" + ex.ToString());
            }

            Console.WriteLine("With HTTP debugging:");
            try {
                Options.HttpDebugging = true;
                Options.HttpFullDebugging = true;
                var graph = endpoint.QueryWithResultGraph(query);
                PrintGraph(graph);
            }
            catch (Exception ex) {
                Console.WriteLine("EXCEPTION:\n" + ex.ToString());
            }
        }

        private static void PrintGraph(IGraph graph)
        {
            if (graph != null) {
                using (var stringWriter = new System.IO.StringWriter()) {
                    var turtleWriter = new TurtleWriter();
                    turtleWriter.PrettyPrintMode = true;
                    turtleWriter.Save(graph, stringWriter);
                    Console.WriteLine("Graph:\n\n" + stringWriter.ToString() + "\n");
                }
            } else {
                Console.WriteLine("Graph is null.");
            }
        }
    }
}

这会产生以下输出：

Without HTTP debugging:
EXCEPTION:
VDS.RDF.Parsing.RdfParseException: [Line 1 Column 9] Unexpected Character (Code 114) r was encountered
   bei VDS.RDF.Parsing.Tokens.NTriplesTokeniser.GetNextToken()
   bei VDS.RDF.Parsing.Tokens.BufferedTokenQueue.BufferInternal()
   bei VDS.RDF.Parsing.Tokens.BufferedTokenQueue.InitialiseBuffer(Int32 amount)
   bei VDS.RDF.Parsing.NTriplesParser.Parse(TokenisingParserContext context)
   bei VDS.RDF.Parsing.NTriplesParser.Load(IRdfHandler handler, TextReader input)
   bei VDS.RDF.Parsing.NTriplesParser.Load(IRdfHandler handler, StreamReader input)
   bei VDS.RDF.Query.SparqlRemoteEndpoint.QueryWithResultGraph(IRdfHandler handler, String sparqlQuery)
   bei VDS.RDF.Query.SparqlRemoteEndpoint.QueryWithResultGraph(String sparqlQuery)
   bei DotNetRdfParsingError.Program.Main(String[] args) in c:\Users\uname\Documents\Test\DOTNET\DotNetRdfParsingError\DotNetRdfParsingError\Program.cs:Zeile 43.
With HTTP debugging:
# HTTP DEBUGGING #
HTTP Request to http://dbpedia.org/sparql?query=PREFIX%20rdf%3A%20%20%3Chttp%3A%2F%2Fwww.w3.org%2F1999%2F02%2F22-rdf-syntax-ns%23%3E%0APREFIX%20rdfs%3A%20%3Chttp%3A%2F%2Fwww.w3.org%2F2000%2F01%2Frdf-schema%23%3E%0APREFIX%20xsd%3A%20%20%3Chttp%3A%2F%2Fwww.w3.org%2F2001%2FXMLSchema%23%3E%0APREFIX%20temp%3A%20%3Chttp%3A%2F%2Fwww.example.com%2Ftemp%2F%3E%0A%0ACONSTRUCT%20%7B%0A%20%20%3Fv1%20a%20temp%3Ar.%0A%20%20%3Fv1%20temp%3Ap0%20%3Fv2.%0A%7D%0AWHERE%20%7B%0A%20%20OPTIONAL%20%7B%0A%20%20%20%20%7B%0A%20%20%20%20%20%20%7B%0A%20%20%20%20%20%20%20%20SELECT%20%3Fv1%0A%20%20%20%20%20%20%20%20WHERE%20%7B%0A%20%20%20%20%20%20%20%20%20%20%3Fv1%20rdfs%3Acomment%20%3Fv2.%0A%20%20%20%20%20%20%20%20%7D%0A%20%20%20%20%20%20%20%20LIMIT%2010%0A%20%20%20%20%20%20%7D.%0A%20%20%20%20%20%20%3Fv1%20rdfs%3Acomment%20%3Fv2.%0A%20%20%20%20%7D.%0A%20%20%7D.%0A%7D

GET
Accept:text/plain,text/ntriples,text/ntriples+turtle,application/rdf-triples,application/x-ntriples,text/plain,text/ntriples,text/ntriples+turtle,application/rdf-triples,application/x-ntriples,text/turtle,application/x-turtle,application/turtle,text/turtle,application/x-turtle,application/turtle,text/n3,text/rdf+n3,text/n3,text/rdf+n3,application/rdf+xml,text/xml,application/xml,application/rdf+xml,text/xml,application/xml,application/json,text/json,application/rdf+json,application/json,text/json,application/rdf+json,text/html,application/xhtml+xml,text/html,application/xhtml+xml,*/*;q=0.5


HTTP Response from http://dbpedia.org/sparql?query=PREFIX%20rdf%3A%20%20%3Chttp%3A%2F%2Fwww.w3.org%2F1999%2F02%2F22-rdf-syntax-ns%23%3E%0APREFIX%20rdfs%3A%20%3Chttp%3A%2F%2Fwww.w3.org%2F2000%2F01%2Frdf-schema%23%3E%0APREFIX%20xsd%3A%20%20%3Chttp%3A%2F%2Fwww.w3.org%2F2001%2FXMLSchema%23%3E%0APREFIX%20temp%3A%20%3Chttp%3A%2F%2Fwww.example.com%2Ftemp%2F%3E%0A%0ACONSTRUCT%20%7B%0A%20%20%3Fv1%20a%20temp%3Ar.%0A%20%20%3Fv1%20temp%3Ap0%20%3Fv2.%0A%7D%0AWHERE%20%7B%0A%20%20OPTIONAL%20%7B%0A%20%20%20%20%7B%0A%20%20%20%20%20%20%7B%0A%20%20%20%20%20%20%20%20SELECT%20%3Fv1%0A%20%20%20%20%20%20%20%20WHERE%20%7B%0A%20%20%20%20%20%20%20%20%20%20%3Fv1%20rdfs%3Acomment%20%3Fv2.%0A%20%20%20%20%20%20%20%20%7D%0A%20%20%20%20%20%20%20%20LIMIT%2010%0A%20%20%20%20%20%20%7D.%0A%20%20%20%20%20%20%3Fv1%20rdfs%3Acomment%20%3Fv2.%0A%20%20%20%20%7D.%0A%20%20%7D.%0A%7D
HTTP/1.1 200 OK

Connection:keep-alive
Vary:Accept-Encoding
Accept-Ranges:bytes
Content-Length:5451
Content-Type:text/plain
Date:Fri, 18 Oct 2013 08:06:33 GMT
Server:Virtuoso/07.00.3204 (Linux) i686-generic-linux-glibc212-64  VDB

@prefix rdf:    <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix ns1:    <http://www.example.com/temp/> .
<http://dbpedia.org/resource/American_Legion_Field_(Florence)>  rdf:type    ns1:r ;
    ns1:p0  "American Legion Field is a baseball venue in Florence, South Carolina, USA. It is home to the Florence Red Wolves of the Coastal Plain League, a collegiate summer baseball league. The Red Wolves have played at the field since 1998. The venue was built sometime before 1981 and has a capacity of 3,500. The field's dimensions are 305 ft. down the foul lines, 335 ft. to the gaps, and 385 ft. to dead center field."@en .
@prefix dbpedia:    <http://dbpedia.org/resource/> .
dbpedia:Francisco_Bautista  rdf:type    ns1:r ;
    ns1:p0  "Francisco Bautista Cuamatzi is a male long-distance runner from Mexico. He represented his native country at the 2008 Summer Olympics in Beijing, PR China, where he finished in 66th place in the men's marathon event, clocking 2:29.28. Rojas set his personal best in the marathon on March 7, 2004 in Torre\u00F3n."@en ,
        "Francisco Bautista ist ein mexikanischer Marathonl\u00E4ufer. Bei den Halbmarathon-Weltmeisterschaften 1999 in Palermo kam er auf den 87. Platz. Im Jahr darauf wurde er F\u00FCnfter beim Marat\u00F3n de la Comarca Lagunera und Achter beim Mailand-Marathon. 2001 wurde er Sechster in der Comarca Lagunera, Zentralamerika/Karibik-Vizemeister im Halbmarathon, belegte bei den Leichtathletik-Weltmeisterschaften in Edmonton Rang 66 und gewann den Monterrey-Marathon."@de .
<http://dbpedia.org/resource/Tillandsia_\u0027Comet\u0027>  rdf:type    ns1:r ;
    ns1:p0  "'Comet' is a hybrid cultivar of the genus Tillandsia in the Bromeliad family."@en .
dbpedia:Glass_Sky   rdf:type    ns1:r ;
    ns1:p0  "Glass Sky is a Japanese manga anthology written and illustrated by Yugi Yamada. It is licensed in North America by Digital Manga Publishing, which released the manga through its June imprint, on December 12, 2007."@en .
dbpedia:Healthcare_in_Guntur    rdf:type    ns1:r ;
    ns1:p0  "The region of Guntur has many health care facilities supported by both the government and private institutions. It is one of the major cities on the east coast region of India in providing excellent medical and health care facilities."@en .
dbpedia:Lake_Nuijamaa   rdf:type    ns1:r ;
    ns1:p0  "Lake Nuijamaa is a lake on the border between Finland and Russia next to the town of Nuijamaa. It is part of the Saimaa Canal linking Vyborg Bay in the Baltic Sea to Lake Saimaa in the Finnish Lakeland."@en ,
        "\u041D\u0443\u0439\u044F\u043C\u0430\u044F\u0440\u0432\u0438\u00A0\u2014 \u043E\u0437\u0435\u0440\u043E \u043D\u0430 \u041A\u0430\u0440\u0435\u043B\u044C\u0441\u043A\u043E\u043C \u043F\u0435\u0440\u0435\u0448\u0435\u0439\u043A\u0435 \u043D\u0430 \u0433\u0440\u0430\u043D\u0438\u0446\u0435 \u0424\u0438\u043D\u043B\u044F\u043D\u0434\u0438\u0438 \u0438 \u0420\u043E\u0441\u0441\u0438\u0438. \u041E\u0437\u0435\u0440\u043E \u0440\u0430\u0441\u043F\u043E\u043B\u043E\u0436\u0435\u043D\u043E \u0432 20 \u043A\u043C \u043D\u0430 \u044E\u0433\u043E-\u0432\u043E\u0441\u0442\u043E\u043A \u043E\u0442 \u0444\u0438\u043D\u0441\u043A\u043E\u0433\u043E \u0433\u043E\u0440\u043E\u0434\u0430 \u041B\u0430\u043F\u043F\u0435\u044D\u043D\u0440\u0430\u043D\u0442\u0430 \u0438 \u0432 26\u00A0\u043A\u043C \u043D\u0430 \u0441\u0435\u0432\u0435\u0440\u043E-\u0437\u0430\u043F\u0430\u0434 \u043E\u0442 \u0440\u043E\u0441\u0441\u0438\u0439\u0441\u043A\u043E\u0433\u043E \u0412\u044B\u0431\u043E\u0440\u0433\u0430. \u0427\u0435\u0440\u0435\u0437 \u043D\u0435\u0433\u043E \u043F\u0440\u043E\u0445\u043E\u0434\u0438\u0442 \u0421\u0430\u0439\u043C\u0435\u043D\u0441\u043A\u0438\u0439 \u043A\u0430\u043D\u0430\u043B."@ru .
dbpedia:Michelangelo_Unterberger    rdf:type    ns1:r ;
    ns1:p0  "Michelangelo Unterberger (August 11, 1695 \u2013 June 27, 1758), was an Austrian painter. Unterberger was born at Cavalese, in what was then Austrian Tyrol, and was part of an Austrian family of artists. He was originally taught by Giuseppe Alberti, and painted primarily religious-themed works."@en ,
        "Michelangelo Unterberger, auch Michael Angelo Unterberger und Michelangelo Unterperger war ein S\u00FCdtiroler Maler des Barock."@de ,
        "Michelangelo Unterberger, aussi Michael Angelo Unterberger ou Michelangelo Unterperger est un peintre autrichien, originaire de la province autonome de Bolzano, et de l'\u00E9poque baroque."@fr .
<http://dbpedia.org/resource/Miroslav_Ivani%C5%A1evi%C4%87> rdf:type    ns1:r ;
    ns1:p0  "Miroslav Ivani\u0161evi\u0107 is a Montenegrin politician. He was appointed as the Montenegrin Minister of Finance in 1998. In 2007 he was accused of being involved in cigarette smuggling into Italy, but was found not guilty in 2010."@en .
dbpedia:Skin_for_Skin   rdf:type    ns1:r ;
    ns1:p0  "Skin for Skin \u00E8 per ora l'ultimo album pubblicato dalla heavy/christian metal band Bride, nel 2006."@it ,
        "Skin for Skin \u00E9 um \u00E1lbum da banda de heavy metal Bride, lan\u00E7ado em 2006 pela gravadora Retrospective Records. A banda sai de seu estilo alternativo e lan\u00E7a um [disco extremamente pesado e totalmente heavy metal.]"@pt ,
        "Skin for Skinis the twelfth studio album by the rock band Bride."@en .
<http://dbpedia.org/resource/Union_Church_(Buckfield,_Maine)>   rdf:type    ns1:r ;
    ns1:p0  "Union Church is a historic church off ME 140 in Buckfield, Maine. It was built in 1832 and added to the National Register of Historic Places in 1980."@en .

# END HTTP DEBUGGING #
Graph:

@base <http://dbpedia.org/sparql>.

@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>.
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>.
@prefix xsd: <http://www.w3.org/2001/XMLSchema#>.

从那里可以看出，结果图仅包含一些前缀，但不包含任何节点或三元组。

异常指向结果图的第 1 行第 9 列，当查看收到的响应时，它将是rdf前缀声明的前缀的开头

@prefix rdf:    <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .

我觉得奇怪的一件事是异常是由NTriplesTokeniser内部的某个地方引发的NTriplesParser，但返回的图形在我看来像Turtle而不是N-Triples

我正在使用来自 NuGet 的最新 dotNetRDF 版本，目前是 1.0.1.2809。

我在那里做错了什么，或者在这种情况下是否需要对 dotNetRDF 进行任何其他设置？

编辑：为了完整起见，我应该在带有一些 DBpedia 数据的本地 Virtuoso 安装中添加，没有崩溃。

4

1 回答 1

4

是的，看起来 DBPedia 做错了事情，出于某种原因，返回 Turtle 时使用的是Content-Typeoftext/plain而不是 Turtle 的适当值，即application/turtle. 因此，为什么 dotNetRDF 选择 NTriples 解析器然后遇到问题。

值得向 DBPedia 人员报告此问题，看看他们是否可以解决此问题

dotNetRDF 可以改进我们形成Accept标题以将text/plain列表放在较低位置的方式，但这仍然不能解决 DBPedia 似乎不正确地进行内容协商的事实。

您可以使用该RdfAcceptHeader属性来解决此问题，如文档所述：

可用于解决不喜欢 dotNetRDF 默认发送的广泛接受标头的错误端点。

例如：

endpoint.RdfAcceptHeader = "application/turtle";

使用此解决方法，给出的代码不会引发异常。

除了 HTTP 调试

关于 HTTP 调试引发不同错误的最后一点，Options.HttpFullDebugging使用响应流，因此解析器接收到已经在末尾的流。

根据解析器的不同，这可能会导致不同的解析错误，但在 NTriples 是文本格式的情况下，空流是有效的空图序列化。该图恰好有一些前缀，因为GraphdotNetRDF 中的实例总是有前缀rdf，rdfs并且xsd默认定义。

于 2013-10-18T10:03:40.643 回答