Ios HTTP POST到SPARQL服务器，返回空HTTP 200

我正在向发送HTTP POST请求

使用此查询：

  string query =
"PREFIX ah: <http://purl.org/artsholland/1.0/>  "
"PREFIX data: <http://data.artsholland.com/>  "
"PREFIX nub: <http://resources.uitburo.nl/>  "
"PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns/>  "
"PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema/>  "
"PREFIX owl: <http://www.w3.org/2002/07/owl/>  "
"PREFIX dc: <http://purl.org/dc/terms/>  "
"PREFIX foaf: <http://xmlns.com/foaf/0.1/>  "
"PREFIX xsd: <http://www.w3.org/2001/XMLSchema/>  "
"PREFIX time: <http://www.w3.org/2006/time/>  "
"PREFIX geo: <http://www.w3.org/2003/01/geo/wgs84_pos/>  "
"PREFIX vcard: <http://www.w3.org/2006/vcard/ns/>  "
"PREFIX osgeo: <http://rdf.opensahara.com/type/geo/>  "
"PREFIX bd: <http://www.bigdata.com/rdf/search/>  "
"PREFIX search: <http://rdf.opensahara.com/search/>  "
"PREFIX fn: <http://www.w3.org/2005/xpath-functions/>  "
"PREFIX gr: <http://purl.org/goodrelations/v1/>  "    
"SELECT ?v ?p ?date ?title ?desc ?modified ?type ?genre  "
"WHERE {  "
    "?v a ah:Venue .  "
    "?p dc:modified ?modified .  "
    "?e ah:venue ?v .  "
    "?e ah:production ?p .  "
    "OPTIONAL {{  "
        "?p dc:title ?title .  "
    "}}  "
    "OPTIONAL {{  "
        "?p ah:shortDescription ?desc .  "
    "}}  "
    "OPTIONAL {{  "
        "?p ah:productionType ?type .  "
    "}}  "
    "OPTIONAL {{  "
        "?p ah:genre ?genre .  "
    "}}  "
    "?v geo:geometry ?geometry .  "
    "FILTER (search:distance(?geometry, \"POINT(4.890        52.3764)\"^^<http://rdf.opensahara.com/type/geo/wkt>) < 2000 *  "  "0.00000898315284) .  "
    "?e time:hasBeginning ?date .  "
    "FILTER (?date >= \"2012-09-06T00:00:00Z\"^^xsd:dateTime) .  "
    "FILTER (?date <= \"2012-09-06T23:59:59Z\"^^xsd:dateTime) .  "
    "} ORDER BY ?v  "
    "LIMIT 100  ";

我得到了一张200元的好票，但没有尸体。我已多次修改查询，但仍然没有有效的返回：

---

使用的库是

我在同一个端点上尝试了SPARQL查询，使用该端点的web界面以及演示密钥和您的密钥，但得到了HTTP 500内部服务器错误，而不是空的HTTP 200响应

当我在可选块中使用正确的名称空间并将{{替换为{时，我确实得到了结果

PREFIX ah: <http://purl.org/artsholland/1.0/>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX owl: <http://www.w3.org/2002/07/owl#>
PREFIX dc: <http://purl.org/dc/terms/>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
PREFIX time: <http://www.w3.org/2006/time#>
PREFIX geo: <http://www.w3.org/2003/01/geo/wgs84_pos#>
PREFIX vcard: <http://www.w3.org/2006/vcard/ns#>
PREFIX osgeo: <http://rdf.opensahara.com/type/geo/>
PREFIX bd: <http://www.bigdata.com/rdf/search#>
PREFIX search: <http://rdf.opensahara.com/search#>
PREFIX fn: <http://www.w3.org/2005/xpath-functions#>
PREFIX gr: <http://purl.org/goodrelations/v1#>
PREFIX gn: <http://www.geonames.org/ontology#>

---

您必须使用这些注释，而不是/在其中一些注释中，这很重要。

那么您的问题是什么？HTTP 200响应表示查询成功；没有正文不是有效的SPARQL JSON结果。您是否尝试过从一个最小的问题开始，然后扩展它？是否尝试将API键作为表单的一部分发送？

PREFIX ah: <http://purl.org/artsholland/1.0/>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX owl: <http://www.w3.org/2002/07/owl#>
PREFIX dc: <http://purl.org/dc/terms/>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
PREFIX time: <http://www.w3.org/2006/time#>
PREFIX geo: <http://www.w3.org/2003/01/geo/wgs84_pos#>
PREFIX vcard: <http://www.w3.org/2006/vcard/ns#>
PREFIX osgeo: <http://rdf.opensahara.com/type/geo/>
PREFIX bd: <http://www.bigdata.com/rdf/search#>
PREFIX search: <http://rdf.opensahara.com/search#>
PREFIX fn: <http://www.w3.org/2005/xpath-functions#>
PREFIX gr: <http://purl.org/goodrelations/v1#>
PREFIX gn: <http://www.geonames.org/ontology#>