当我在Virtuoso SPARQL Query Editor执行时，SPARQL ASK对以下代码执行的true查询会返回<?php
require_once('./sparqllib.php');
$db = sparql_connect('http://dbpedia.org/sparql');
$query = "
ASK {
?book a dbpedia-owl:Book .
?book dbpprop:author ?author .
?book dbpprop:name ?bookname .
?author dbpprop:name ?authorname .
FILTER regex(?bookname, 'A Tale of Two Cities', 'i') .
FILTER regex(?authorname, 'Dickens', 'i')
}";
$result = sparql_query($query);
var_dump($result);
。同样的结果是我想要返回到我的脚本。我如何调整 sparqllib 使用？
var_dump() object(sparql_result)[3]
public 'rows' =>
array (size=0)
empty
public 'fields' =>
array (size=0)
empty
public 'db' =>
object(sparql_connection)[1]
public 'db' => null
public 'debug' => boolean false
public 'errno' => null
public 'error' => null
public 'ns' =>
array (size=0)
empty
public 'params' => null
public 'caps' =>
array (size=0)
empty
public 'caps_desc' =>
array (size=7)
'select' => string 'Basic SELECT' (length=12)
'constant_as' => string 'SELECT ("foo" AS ?bar)' (length=22)
'math_as' => string 'SELECT (2+3 AS ?bar)' (length=20)
'count' => string 'SELECT (COUNT(?a) AS ?n) ?b ... GROUP BY ?b' (length=43)
'max' => string 'SELECT (MAX(?a) AS ?n) ?b ... GROUP BY ?b' (length=41)
'sample' => string 'SELECT (SAMPLE(?a) AS ?n) ?b ... GROUP BY ?b' (length=44)
'load' => string 'LOAD <...>' (length=10)
public 'caps_cache' => null
public 'caps_anysubject' => null
public 'endpoint' => string 'http://dbpedia.org/sparql' (length=25)
public 'i' => int 0
的结果：
{{1}}
答案 0 :(得分：3)
sparqllib.php似乎不支持处理ask查询的结果，所以你应该只使用
select * where {
?book a dbpedia-owl:Book .
?book dbpprop:author ?author .
?book dbpprop:name ?bookname .
?author dbpprop:name ?authorname .
FILTER regex(?bookname, 'A Tale of Two Cities', 'i') .
FILTER regex(?authorname, 'Dickens', 'i')
}
limit 1
并检查您是否得到了结果。
ask结果）我认为sparqllib不支持select查询以外的查询。如果您查看sparqllib.php，可以看到查询的执行方式：
function query( $query, $timeout=null )
{
$prefixes = "";
foreach( $this->ns as $k=>$v )
{
$prefixes .= "PREFIX $k: <$v>\n";
}
$output = $this->dispatchQuery( $prefixes.$query, $timeout );
if( $this->errno ) { return; }
$parser = new xx_xml($output, 'contents');
if( $parser->error() )
{
$this->errno = -1; # to not clash with CURLOPT return; }
$this->error = $parser->error();
return;
}
return new sparql_result( $this, $parser->rows, $parser->fields );
}
dispatchQuery负责发送查询并返回结果。它在application/sparql-results+xml中询问它们，这就是XML解析器参与的原因。如果您查看XML解析代码，可以使用以下内容：
function startXML($parser, $name, $attr)
{
if( $name == "sparql" ) { $this->looks_legit = true; }
if( $name == "result" )
{
$this->result = array();
}
if( $name == "binding" )
{
$this->part = $attr["name"];
}
if( $name == "uri" || $name == "bnode" )
{
$this->part_type = $name;
$this->chars = "";
}
if( $name == "literal" )
{
$this->part_type = "literal";
if( isset( $attr["datatype"] ) )
{
$this->part_datatype = $attr["datatype"];
}
if( isset( $attr["xml:lang"] ) )
{
$this->part_lang = $attr["xml:lang"];
}
$this->chars = "";
}
if( $name == "variable" )
{
$this->fields[] = $attr["name"];
}
}
现在，如果您查看定义结果应该是什么的SPARQL Query Results XML Format (Second Edition)，尤其是2.3.2. Boolean Results，我们会看到ASK查询的结果应该是
<?xml version="1.0"?> <sparql xmlns="http://www.w3.org/2005/sparql-results#"> ... head ... <boolean>true</boolean> </sparql>
sparqllib.php不包含任何要查找名称为“boolean”的元素的内容。它只是为了处理select结果而设计的。也就是说，代码是根据LGPL许可的，并且根据文件头可以在GitHub上获得，所以如果你愿意，你应该能够分叉并添加ask支持：
###############################
# Christopher Gutteridge 2010
# cjg@ecs.soton.ac.uk
# LGPL License
# http://graphite.ecs.soton.ac.uk/sparqllib/
# https://github.com/cgutteridge/PHP-SPARQL-Lib
###############################