SPARQL:一个查询有效; 类似的查询失败

Question

有两个使用W3C pyRdfa提取器的SPARQL查询.

1:此查询产生预期结果:

    PREFIX dc: <http://purl.org/dc/elements/1.1/>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT ?Content ?Author
FROM <http://www.w3.org/2007/08/pyRdfa/extract?uri=http://www.3kbo.com/examples/rdfa/simple.html>
WHERE {
    ?s dc:creator ?o .
    ?s dc:title ?Content .
    ?o foaf:name ?Author .
    }
ORDER BY ?Content

结果如下:

http://www.sparql.org/sparql?query=PREFIX+dc%3A+%3Chttp%3A%2F%2Fpurl.org%2Fdc%2Felements%2F1.1%2F%3E%0D%0APREFIX+foaf%3A+%3Chttp%3A%2F%2Fxmlns.com%2Ffoaf%2F0.1%2F%3E%0D%0ASELECT+%3FContent+%3FAuthor%0D%0AFROM+%3Chttp%3A%2F%2Fwww.w3.org%2F2007%2F08%2FpyRdfa%2Fextract%3Furi%3Dhttp%3A%2F%2Fwww.3kbo.com%2Fexamples%2Frdfa%2Fsimple.html%3E%0D%0AWHERE+{%0D%0A%09%3Fs+dc%3Acreator+%3Fo+.%0D%0A%09%3Fs+dc%3Atitle+%3FContent+.%0D%0A%09%3Fo+foaf%3Aname+%3FAuthor+.%0D%0A%09}%0D%0AORDER+BY+%3FContent&default-graph-uri=&output=text&stylesheet=%2Fxml-to-html.xsl

2:此查询不会产生类似于上面的结果:

PREFIX dc: <http://purl.org/dc/elements/1.1/>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT ?Content ?Author
FROM <http://www.w3.org/2007/08/pyRdfa/extract?uri=http://www.w3.org/2013/Talks/0902-Lisbon-IH/>
WHERE {
    ?s dc:author ?o .
    ?s dc:title ?Content .
    ?o foaf:name ?Author .
    }
ORDER BY ?Content

结果如下:

http://www.sparql.org/sparql?query=PREFIX+dc%3A+%3Chttp%3A%2F%2Fpurl.org%2Fdc%2Felements%2F1.1%2F%3E%0D%0APREFIX+foaf%3A+%3Chttp%3A%2F%2Fxmlns.com%2Ffoaf%2F0.1%2F%3E%0D%0ASELECT+%3FContent+%3FAuthor%0D%0AFROM+%3Chttp%3A%2F%2Fwww.w3.org%2F2007%2F08%2FpyRdfa%2Fextract%3Furi%3Dhttp%3A%2F%2Fwww.w3.org%2F2013%2FTalks%2F0902-Lisbon-IH%2F%3E%0D%0AWHERE+{%0D%0A%09%3Fs+dc%3Aauthor+%3Fo+.%0D%0A%09%3Fs+dc%3Atitle+%3FContent+.%0D%0A%09%3Fo+foaf%3Aname+%3FAuthor+.%0D%0A%09}%0D%0AORDER+BY+%3FContent%0D%0A&default-graph-uri=&output=text&stylesheet=%2Fxml-to-html.xsl

为什么#2无法产生像#1这样的结果？

#2的SPARQL代码中是否有错误？

或者与#1和#2相关的RDFa的结构是否存在语义差异？

我在示例中使用了这个pyRdfa版本:

http://www.w3.org/2007/08/pyRdfa/extract?uri=

不使用偶尔会混淆SPARQL处理器的这个版本:

http://www.w3.org/2012/pyRdfa/extract?uri=

TY为此提供指导.

Answer 1

http://www.w3.org/2013/Talks/0902-Lisbon-IH/使用RDFa 1.1,但http://www.w3.org/2007/08/pyRdfa/extract?uri=支持RDFa 1.0.

您使用的是:

<rdf:RDF
  xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
  xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
  xmlns:xhv="http://www.w3.org/1999/xhtml/vocab#"
  xmlns:xml="http://www.w3.org/XML/1998/namespace"
>
  <rdf:Description rdf:about="talk:">
     <xhv:icon rdf:resource="http://www.w3.org/2001/sw/favicon-sw.png"/>
     <xhv:stylesheet rdf:resource="http://www.w3.org/2006/02/charter-style.css"/>
     <xhv:stylesheet rdf:resource="http://www.w3.org/Guide/pubrules-style.css"/>
     <xhv:copyright rdf:resource="http://creativecommons.org/licenses/by-nd/3.0/"/>
  </rdf:Description>
</rdf:RDF>

即没有三重奏.这是因为源使用RDFa 1.1 @prefix属性声明前缀,这在RDFa 1.0中不存在.因此,大多数缩写的URL根据较旧的解析器而被破坏.

使用较新的解析器,您会发现更多的三元组,包括:

...
talk: a ore:ResourceMap;
dc:author <http://www.ivan-herman.net/foaf#me>;
dc:date "$Date: 2013-08-27 07:51:24 $";
dc:title "Introduction to Linked Open Data";
ore:describes <http://www.w3.org/2012/0902-Lisbon-IH/#talk> .
...

这是你在寻找什么.

然而

作为美中不足的最后一个文件,这两个文件正在使用不同版本的都柏林核心命名空间.RDFa 1.1 默认情况下将dc前缀绑定到更新http://purl.org/dc/terms/,这会抛出您的查询.

所以尝试:

PREFIX dc: <http://purl.org/dc/terms/> # FIXED dc
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT ?Content ?Author
 # Use RDFa 1.1 parser
FROM <http://www.w3.org/2012/pyRdfa/extract?uri=http://www.w3.org/2013/Talks/0902-Lisbon-IH/>
WHERE {
    ?s dc:author ?o .
    ?s dc:title ?Content .
    ?o foaf:name ?Author .
}
ORDER BY ?Content

田田,结果.