Ruby on Rails SPARQL 客户端

Question

我目前正在使用 Ruby on Rails SPARQL 客户端尝试从 dbpedia 上的公共 SPARQL 端点检索信息。我正在运行的通用查询如下：

query = "
      PREFIX dbo: <http://dbpedia.org/ontology/>
      PREFIX prop: <http://dbpedia.org/property/>
      PREFIX foaf: <http://xmlns.com/foaf/0.1/>
      PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
      SELECT * WHERE {
        ?city prop:name 'Antwerpen'@en;
              a dbo:PopulatedPlace;
              dbo:abstract ?abstract .
        FILTER langMatches( lang(?abstract), 'en')
        OPTIONAL { ?city foaf:homepage ?homepage }
        OPTIONAL { ?city rdfs:comment ?comment .
                  FILTER langMatches( lang(?comment), 'en') }
      }"

这是一个通用查询，可从 dbpedia 返回有关城市的一些通用信息。我已经在 sparql 端点上手动测试了它，它检索了我希望它返回的信息。 但是，我似乎找不到在 Ruby on Rails 中解析响应的方法。

目前我正在尝试使用 RDF for Ruby 和 sparql-client。代码如下所示（基于我能找到的示例）：

result = {}
    client = SPARQL::Client.new("http://dbpedia.org/sparql")
    client.query(query).first.each_binding { |name, value| result[name] << value}
    result

但我无法检索任何内容。使用调试器运行手动单步执行变量时，查询一执行就停止，我什至无法查看返回值。

谁有一个关于如何对 SPARQL 端点执行查询并解析响应的好例子？

Answer 1

我刚刚尝试了您的代码（使用 = 而不是

require 'rubygems'
require 'sparql/client'

query = "
  PREFIX dbo: <http://dbpedia.org/ontology/>
  PREFIX prop: <http://dbpedia.org/property/>
  PREFIX foaf: <http://xmlns.com/foaf/0.1/>
  PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
  SELECT * WHERE {
    ?city prop:name 'Antwerpen'@en;
          a dbo:PopulatedPlace;
          dbo:abstract ?abstract .
    FILTER langMatches( lang(?abstract), 'en')
    OPTIONAL { ?city foaf:homepage ?homepage }
    OPTIONAL { ?city rdfs:comment ?comment .
              FILTER langMatches( lang(?comment), 'en') }
  }"

result = {}
client = SPARQL::Client.new("http://dbpedia.org/sparql")
client.query(query).first.each_binding { |name, value| result[name] = value}
p result

当我运行它时：

$ jruby sparql.rb 
{:city=>#<RDF::URI:0x890(http://dbpedia.org/resource/Antwerp)>, :abstract=>#<RDF::Literal:0x892("Antwerp is a city and municipality in Belgium and the capital of the Antwerp province in Flanders, one of Belgium's three regions. Antwerp's total population is 472,071 (as of 1 January 2008) and its total area is 204.51 km, giving a population density of 2,308 inhabitants per km\u00B2. The metropolitan area, including the outer commuter zone, covers an area of 1,449 km with a total of 1,190,769 inhabitants as of 1 January 2008. The nickname of inhabitants of Antwerp is Sinjoren, after the Spanish word se\u00F1or, which means 'mister' or 'gent'. Antwerp has long been an important city in the nations of the Benelux both economically and culturally, especially before the Spanish Fury of the Dutch Revolt. It is located on the right bank of the river Scheldt, which is linked to the North Sea by the estuary Westerschelde."@en)>, :homepage=>#<RDF::URI:0x898(http://www.antwerpen.be/)>, :comment=>#<RDF::Literal:0x89a("Antwerp is a city and municipality in Belgium and the capital of the Antwerp province in Flanders, one of Belgium's three regions. Antwerp's total population is 472,071 (as of 1 January 2008) and its total area is 204.51 km, giving a population density of 2,308 inhabitants per km\u00B2. The metropolitan area, including the outer commuter zone, covers an area of 1,449 km with a total of 1,190,769 inhabitants as of 1 January 2008."@en)>}

根据您的描述，可能是您遇到了连接问题，或者 dbpedia 可能已超载。