为什么RDF看起来如此复杂

Question

所以这是一个rdf格式的条目.我想理解为什么它的某些部分看起来如此复杂.

<pgterms:file rdf:about="&f;dirs/3/1/9/0/31900/31900-8.zip">
  <dc:format><dcterms:IMT><rdf:value>text/plain; charset="iso-8859-1"</rdf:value></dcterms:IMT></dc:format>
  <dc:format><dcterms:IMT><rdf:value>application/zip</rdf:value></dcterms:IMT></dc:format>
  <dcterms:extent>193120</dcterms:extent>
  <dcterms:modified><dcterms:W3CDTF><rdf:value>2010-04-06</rdf:value></dcterms:W3CDTF></dcterms:modified>
  <dcterms:isFormatOf rdf:resource="#etext31900" />
</pgterms:file>

特别是,这个值:

<dc:format><dcterms:IMT><rdf:value>text/plain; charset="iso-8859-1"</rdf:value></dcterms:IMT></dc:format>

为什么它既需要dcterms:IMTAND 又需要rdf:value一部分？对于看似没什么实际效益的看起来似乎很臃肿.因为它已经在使用MIME类型,所以对我来说没有意义.

Answer 1

为什么xml有这么多尖括号我的眼睛受伤....因为它本来是由解析器而不是人类阅读.

你的样本不是rdf(rdf是框架),它是rdf/xml,是框架中图形的一种可能的序列化. Turtle/n3是更漂亮的序列化.N-Triples非常简单.

一些非常小的例子,不包括任何真实的细节,但......

RDF/XML:

<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
         xmlns:dc="http://purl.org/dc/elements/1.1/">
  <rdf:Description rdf:about="http://www.w3.org/2001/sw/RDFCore/ntriples/">
    <dc:creator>Art Barstow</dc:creator>
    <dc:creator>Dave Beckett</dc:creator>
    <dc:publisher rdf:resource="http://www.w3.org/"/>
  </rdf:Description>
</rdf:RDF>

的N-Triples

<http://www.w3.org/2001/sw/RDFCore/ntriples/> <http://purl.org/dc/elements/1.1/creator> "Dave Beckett" .
<http://www.w3.org/2001/sw/RDFCore/ntriples/> <http://purl.org/dc/elements/1.1/creator> "Art Barstow" .
<http://www.w3.org/2001/sw/RDFCore/ntriples/> <http://purl.org/dc/elements/1.1/publisher> <http://www.w3.org/> .

N3

@prefix dc: <http://purl.org/dc/elements/1.1/>

<http://www.w3.org/2001/sw/RDFCore/ntriples/> 
     dc:creator "Dave Beckett";
     dc:creator "Art Barstow";
     dc:publisher <http://www.w3.org/>.

编辑:你可以停止阅读,这只是OP在不同序列化中提供的示例.回答这个问题

为什么它同时需要dcterms:IMT和rdf:value部分？

当存在"空节点"时,rdf/xml必须执行某种断续步骤.你可以在下面看到N-Triples写出空白节点,而n3试图让关系变得更加明显.所有这些都是相同rdf图的序列化.

稍微修改了RDF/XML(添加了名称空间),因此它解析:

<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
         xmlns:dc="http://purl.org/dc/elements/1.1/"
         xmlns:dcterms="http://purl.org/dc/terms/"
         xmlns:pgterms="http://www.gutenberg.org/rdfterms/">
<pgterms:file rdf:about="/home/me/dirs/3/1/9/0/31900/31900-8.zip">
  <dc:format><dcterms:IMT><rdf:value>text/plain; charset="iso-8859-1"</rdf:value></dcterms:IMT></dc:format>
  <dc:format><dcterms:IMT><rdf:value>application/zip</rdf:value></dcterms:IMT></dc:format>
  <dcterms:extent>193120</dcterms:extent>
  <dcterms:modified><dcterms:W3CDTF><rdf:value>2010-04-06</rdf:value></dcterms:W3CDTF></dcterms:modified>
  <dcterms:isFormatOf rdf:resource="#etext31900" />
</pgterms:file>
</rdf:RDF>

的N-Triples

</home/me/dirs/3/1/9/0/31900/31900-8.zip> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.gutenberg.org/rdfterms/file> .
</home/me/dirs/3/1/9/0/31900/31900-8.zip> <http://purl.org/dc/elements/1.1/format> _:LqSOByLi19 .
</home/me/dirs/3/1/9/0/31900/31900-8.zip> <http://purl.org/dc/elements/1.1/format> _:LqSOByLi20 .
</home/me/dirs/3/1/9/0/31900/31900-8.zip> <http://purl.org/dc/terms/isFormatOf> <#etext31900> .
</home/me/dirs/3/1/9/0/31900/31900-8.zip> <http://purl.org/dc/terms/modified> _:LqSOByLi21 .
</home/me/dirs/3/1/9/0/31900/31900-8.zip> <http://purl.org/dc/terms/extent> "193120" .
_:LqSOByLi21 <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://purl.org/dc/terms/W3CDTF> .
_:LqSOByLi21 <http://www.w3.org/1999/02/22-rdf-syntax-ns#value> "2010-04-06" .
_:LqSOByLi20 <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://purl.org/dc/terms/IMT> .
_:LqSOByLi20 <http://www.w3.org/1999/02/22-rdf-syntax-ns#value> "application/zip" .
_:LqSOByLi19 <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://purl.org/dc/terms/IMT> .
_:LqSOByLi19 <http://www.w3.org/1999/02/22-rdf-syntax-ns#value> "text/plain; charset=\"iso-8859-1\"" .

N3 /龟

@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix dc: <http://purl.org/dc/elements/1.1/> .
@prefix dcterms: <http://purl.org/dc/terms/> .
@prefix pgterms: <http://www.gutenberg.org/rdfterms/> .

</home/me/dirs/3/1/9/0/31900/31900-8.zip> a pg:file;
    dc:format 
        [ a dcterms:IMT;  rdf:value "text/plain; charset=\"iso-8859-1\"" ],
        [ a dcterms:IMT;  rdf:value "application/zip" ];
    dcterms:extent "193120";
    dcterms:isFormatOf <#etext31900>;
    dcterms:modified [ a dcterms:W3CDTF; rdf:value "2010-04-06" ] .

注意:如果它是彩色的, N3甚至更漂亮

编辑2: 上面描述了有一个bnode但是为什么有一个.... 上面N3序列化dcterms:modified的最后一行中的谓词可以(我希望)更像是:

dcterms:modified "2010-04-06"^^dcterms:W3CDTF
# vs
dcterms:modified [ a dcterms:W3CDTF; rdf:value "2010-04-06" ]

rdf:value甚至存在的原因是三倍:

exproduct:item10245   exterms:weight   [rdf:value        "2.4"^^xsd:decimal
                                        exterms:units    exunits:kilograms] .

除了单元之外,节点还可以指示object三元组的精度或其他特征.

是的,我有点讨厌rdf:value破坏理解和实践的东西,有利于认识论的纯洁.