正确地通过httr为SPARQL公共可用端点发出POST查询

Question

我试图使用通过statistics.gov.scot提供的SPARQL端点获取一些公开可用的数据。API页面建议使用POST。

选项1: POST (推荐)向端点发出一个POST，其中包含正文中的查询，以及sparql-+json的接受头： POST http://statistics.gov.scot/sparql HTTP/1.1主机: statistics.gov.scot接受:statistics.gov.scot/sparql-结果+json内容-类型:application/x表单-urlencoded statistics.gov.scot

问题

我试图以以下方式运行查询，该查询将生成一个具有可用地理位置的表：

  response <- httr::POST(
    url = "http://statistics.gov.scot/sparql.csv",
    query = "PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>  
             SELECT  ?hierarchy ?label 
                WHERE {   ?hierarchy  
                           rdfs:subPropertyOf     
                              <http://statistics.gov.scot/def/hierarchy/best-fit>  ;  
                            rdfs:label ?label } ")

结果返回错误响应的代码：

 httr::status_code(response)
[1] 400

查询

当对基于web的enpoint接口(https://statistics.gov.scot/sparql-beta)进行测试时，查询工作得很好。

PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>  
SELECT  ?hierarchy  ?label 
 WHERE {   
  ?hierarchy  
  rdfs:subPropertyOf  <http://statistics.gov.scot/def/hierarchy/best-fit>  ;
  rdfs:label ?label }

Answer 1

JSON

response <- httr::POST(
    url = "http://statistics.gov.scot/sparql", accept("application/sparql-results+json"),
    body = list( query = "SELECT * { ?s ?p ?o } LIMIT 10" )
    )
content(response, "text")

或(特定端点)

response <- httr::POST(
    url = "http://statistics.gov.scot/sparql.json",
    body = list( query = "SELECT * { ?s ?p ?o } LIMIT 10" )
    )
content(response, "text")

CSV

response <- httr::POST(
    url = "http://statistics.gov.scot/sparql", accept("text/csv"),
    body = list( query = "SELECT * { ?s ?p ?o } LIMIT 10" )
    )
content(response, "text")

或(特定端点)

response <- httr::POST(
    url = "http://statistics.gov.scot/sparql.csv",
    body = list( query = "SELECT * { ?s ?p ?o } LIMIT 10" )
    )
content(response, "text")