PHP EasyRDF：无法从构造查询中获取图形

Question

我正在尝试从通过 EasyRdf_Sparql_Client::query 发送的查询中获取 EasyRdf_Graph 对象。

SELECT and ASK queries will return an object of type EasyRdfSparqlResult.

CONSTRUCT and DESCRIBE queries will return an object of type EasyRdf_Graph.

这是我的代码：

<?php
require APPPATH .'third_party/vendor/autoload.php';        
$endpointUrl = "http://data.bnf.fr/sparql";        
$dummyConstructQueryString = "construct { ?s ?q ?r } where { ?s ?p ?o . ?o ?q ?r } limit 1";        
$endPoint = new EasyRdf_Sparql_Client($endpointUrl);
$result = $endPoint->query($dummyConstructQueryString);                
var_dump($result);
echo $result;
?>

这是输出，如您所见，它是 EasyRdf_Sparql_Result:

object(**EasyRdf_Sparql_Result**)#47 (6) {
  ["type":"EasyRdf_Sparql_Result":private]=>
  string(8) "bindings"
  ["boolean":"EasyRdf_Sparql_Result":private]=>
  NULL
  ["ordered":"EasyRdf_Sparql_Result":private]=>
  NULL
  ["distinct":"EasyRdf_Sparql_Result":private]=>
  NULL
  ["fields":"EasyRdf_Sparql_Result":private]=>
  array(3) {
    [0]=>
    string(1) "s"
    [1]=>
    string(1) "p"
    [2]=>
    string(1) "o"
  }
  ["storage":"ArrayIterator":private]=>
  array(1) {
    [0]=>
    object(stdClass)#48 (3) {
      ["s"]=>
      object(EasyRdf_Resource)#49 (2) {
        ["uri":protected]=>
        string(56) "http://www.w3.org/ns/sparql-service-description#endpoint"
        ["graph":protected]=>
        NULL
      }
      ["p"]=>
      object(EasyRdf_Resource)#50 (2) {
        ["uri":protected]=>
        string(47) "http://www.w3.org/1999/02/22-rdf-syntax-ns#type"
        ["graph":protected]=>
        NULL
      }
      ["o"]=>
      object(EasyRdf_Resource)#51 (2) {
        ["uri":protected]=>
        string(42) "http://www.w3.org/2000/01/rdf-schema#Class"
        ["graph":protected]=>
        NULL
      }
    }
  }
}
+-------------+----------+------------+
| ?s          | ?p       | ?o         |
+-------------+----------+------------+
| sd:endpoint | rdf:type | rdfs:Class |

也尝试了不同的端点（http://dbpedia.org/sparql and ~~http://localhost:3030/testFuseki~~) because I saw this issue : https://github.com/njh/easyrdf/issues/226，但都是一样的。

关于安装的信息

随 Composer 安装的 EasyRDF 版本 0.9.1
PHP 版本 7.0.30-0+deb9u1 + Apache/2.4.25 (Debian)

任何线索将不胜感激，提前致谢。

编辑

实际上它适用于我本地安装的 Fuseki。由于 http://data.bnf/fr/sparql and http://dbpedia.org/sparql 都是 Virtuoso 端点，我想知道问题是否仅与 Virtuoso 有关。

Answer 1

感谢 Ted 关于 headers 和更新 EasyRDF 的建议，我在阅读了更多有关 EasyRDF 问题 #226 的信息后找到了 a solution。问题是它需要 re-write php 代码才能使用新的命名空间等。如果有人知道 0.9.1 版本的解决方案，那将非常有帮助！

似乎返回的object类型（EasyRdf_Graph/EasyRdf_Sparql_Result）取决于headers的Accept参数。我试图通过 Firebug 和 re-send 请求修改它（添加 Virtuoso doc 中列出的不同 content-types ），但没有得到任何 EasyRdf_Graph object 还与 Virtuoso。

正如 Ted 所问，这里是请求 headers 的相关部分（使用上述 php 代码和 EasyRDF 0.0.1）：

Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: fr,fr-FR;q=0.8,en-US;q=0.5,en;q=0.3
Accept-Encoding: gzip, deflate
Connection: keep-alive

为了获得端点响应 headers，我添加了这一行：

print_r(get_headers($endpointUrl));

这是对 Fuseki 的响应 headers（给出 EasyRdf_Graph object）：

[0] => HTTP/1.1 200 OK
[1] => Date: Tue, 11 Sep 2018 06:14:56 GMT
[2] => Fuseki-Request-ID: 13
[3] => Vary: Accept,Accept-Encoding,Accept-Charset
[4] => Content-Type: application/n-quads
[5] => Vary: User-Agent

对于 Virtuoso (http://data.bnf.fr)

[0] => HTTP/1.1 302 Found
[1] => Date: Tue, 11 Sep 2018 06:12:29 GMT
[2] => Server: Apache
[3] => Location: http://data.bnf.fr/sparql/
[4] => Content-Length: 210
[5] => Content-Type: text/html; charset=iso-8859-1
[6] => Vary: Accept-Encoding,User-Agent
[7] => Connection: close
[8] => HTTP/1.1 200 OK
[9] => Date: Tue, 11 Sep 2018 06:12:29 GMT
[10] => Server: Apache
[11] => Last-Modified: Mon, 19 Feb 2018 10:34:21 GMT
[12] => ETag: "200036-3a99-5658e3ca8a540"
[13] => Accept-Ranges: bytes
[14] => Content-Length: 15001
[15] => Vary: Accept-Encoding,User-Agent
[16] => Access-Control-Allow-Origin: *
[17] => Content-Type: text/html
[18] => Content-Language: fr
[19] => Connection: close

N.B。 : 对于 data.bnf.fr，代码是 302（重定向），但似乎没有任何区别，请参阅 dbpedia 响应：

[0] => HTTP/1.1 200 OK
[1] => Date: Tue, 11 Sep 2018 07:17:23 GMT
[2] => Content-Type: text/html; charset=UTF-8
[3] => Content-Length: 14172
[4] => Connection: close
[5] => Vary: Accept-Encoding
[6] => Server: Virtuoso/07.20.3229 (Linux) i686-generic-linux-glibc25-64  VDB
[7] => Expires: Tue, 18 Sep 2018 07:17:23 GMT
[8] => Cache-Control: max-age=604800
[9] => Access-Control-Allow-Origin: *
[10] => Access-Control-Allow-Credentials: true
[11] => Access-Control-Allow-Methods: GET, POST, OPTIONS
[12] => Access-Control-Allow-Headers: DNT,X-CustomHeader,Keep-Alive,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Accept-Encoding
[13] => Accept-Ranges: bytes

所以这里是 解决方案，使用新的 php 代码和作曲家更新 来获取 EasyRDF dev-master :

1) 编辑 composer.json :

{
    "require": {
        "easyrdf/easyrdf": "dev-master"
    }
}

2) 运行

php composer.phar update

3) 重写 php 代码：

require_once './third_party/vendor/autoload.php';
$endpointUrl = "http://data.bnf.fr/sparql";        
$dummyConstructQueryString = "construct { ?s ?q ?r } where { ?s ?p ?o . ?o ?q ?r } limit 1";        
$endPoint = new \EasyRdf\Sparql\Client($endpointUrl); // <-- here use the namespace
$result = $endPoint->query($dummyConstructQueryString);                
var_dump($result);

编辑

最后我不确定http请求headers参数"Accept"是否是获得EasyRdf_Graphobject的条件。这里是 headers 用于更新 Easyrdf 代码（"dev-master" 版本）的请求和响应。也许 EasyRDF 解析查询和结果来构建一个 EasyRdf_Graph object。

要求

 Host: localhost
 User-Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:62.0) Gecko/20100101 Firefox/62.0
 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
 Accept-Language: fr,fr-FR;q=0.8,en-US;q=0.5,en;q=0.3
 Accept-Encoding: gzip, deflate
 DNT: 1
 Connection: keep-alive
 Upgrade-Insecure-Requests: 1
 Cache-Control: max-age=0

来自 http://data.bnf.fr/sparql/ 的回应（通过 print_r(get_headers($endpointUrl)); 获得）

 [0] => HTTP/1.1 302 Found
 [1] => Date: Wed, 12 Sep 2018 06:21:48 GMT
 [2] => Server: Apache
 [3] => Location: http://data.bnf.fr/sparql/
 [4] => Content-Length: 210
 [5] => Content-Type: text/html; charset=iso-8859-1
 [6] => Vary: Accept-Encoding,User-Agent
 [7] => Connection: close
 [8] => HTTP/1.1 200 OK
 [9] => Date: Wed, 12 Sep 2018 06:21:48 GMT
 [10] => Server: Apache
 [11] => Last-Modified: Mon, 19 Feb 2018 10:34:21 GMT
 [12] => ETag: "200036-3a99-5658e3ca8a540"
 [13] => Accept-Ranges: bytes
 [14] => Content-Length: 15001
 [15] => Vary: Accept-Encoding,User-Agent
 [16] => Access-Control-Allow-Origin: *
 [17] => Content-Type: text/html
 [18] => Content-Language: fr
 [19] => Connection: close

Answer 2

EasyRDF 发出并张贴在您的答案中的 HTTP 请求 header 揭示了这个问题（所有这些额外的细节实际上都应该编辑到您的问题中）。

EasyRDF请求header --

Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8

-- 表示 EasyRDF 同样乐意接收 text/html 或 application/xhtml+xml，然后会更喜欢 application/xml，其次是 */* 或 "any media type" .

其实不然！ text/html 不是 EasyRDF 想要的，在这种情况下它绝对不是 just-as-good 和 application/xhtml+xml 也不比 application/xml 好。

也就是说，Virtuoso 完全按照 EasyRDF 的要求进行，并提供 text/html ... EasyRDF 毫不奇怪地没有将其视为图形。

从 Fuseki 返回的内容（application/n-quads，这不是 EasyRDF 请求的任何特定 MIME 类型）

EasyRDF 应该请求某些 RDF MIME 类型（例如 text/turtle、application/rdf+xml、application/trig、application/n-triples, application/n-quads, application/ld+json, sparql-results+xml ... EasyRDF 实际上并不支持所有这些，所以这个列表不应该简单地放入 Accept: header). EasyRDF 还应该指出这些（可能具有内部优先顺序）优于任何 non-RDF MIME 类型（包括 EasyRDF 当前请求的所有特定 MIME 类型）或通配符（*/*）。

这应该是 reported as a bug in EasyRDF. Feel free to tag me (@TallTed on github) 在你的报告中。

PHP EasyRDF：无法从构造查询中获取图形

PHP EasyRDF : unable to get graph from construct query

sparql

virtuoso

fuseki

easyrdf