我正在尝试使用Haskell库RDF4H解析RDF / XML文件。我可以使用以下函数解析文件：
parseRDFXML :: String -> IO (Either ParseFailure (RDF TList))
parseRDFXML = parseFile (XmlParser Nothing Nothing)
parseRDFXML' :: String -> IO (Either ParseFailure (RDF AdjHashMap))
parseRDFXML' = parseFile (XmlParser Nothing Nothing)
然后使用ghci检查生成的内容：
parsed <- parseRDFXML "testRDF.xml"
result = fromEither parsed
result
它将打印它被解析的三元组。但是，某些字段似乎缺失。例如，我没有看到dcterms:subject字段或dcterms:language字段。
我做错了吗？
作为参考，这里是我试图解析的RDF数据类型的一个例子：
<?xml version="1.0" encoding="utf-8"?>
<rdf:RDF xml:base="http://www.gutenberg.org/"
xmlns:dcam="http://purl.org/dc/dcam/"
xmlns:dcterms="http://purl.org/dc/terms/"
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:cc="http://web.resource.org/cc/"
xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
xmlns:pgterms="http://www.gutenberg.org/2009/pgterms/"
>
<pgterms:ebook rdf:about="ebooks/15233">
<dcterms:language>
<rdf:Description rdf:nodeID="N30b5232d06364953b02811ebc0debbb9">
<rdf:value rdf:datatype="http://purl.org/dc/terms/RFC4646">en</rdf:value>
</rdf:Description>
</dcterms:language>
<dcterms:subject>
<rdf:Description rdf:nodeID="N83c641d289c446b685ac37fd15845219">
<dcam:memberOf rdf:resource="http://purl.org/dc/terms/LCC"/>
<rdf:value>DA</rdf:value>
</rdf:Description>
</dcterms:subject>
<dcterms:type>
<rdf:Description rdf:nodeID="N23dc05dbba734cf28488df2f004510ea">
<rdf:value>Text</rdf:value>
<dcam:memberOf rdf:resource="http://purl.org/dc/terms/DCMIType"/>
</rdf:Description>
</dcterms:type>
<dcterms:subject>
<rdf:Description rdf:nodeID="N2b00277514604edc806f20cd6a653ba6">
<dcam:memberOf rdf:resource="http://purl.org/dc/terms/LCSH"/>
<rdf:value>Nelson, Horatio Nelson, Viscount, 1758-1805 -- Death and burial</rdf:value>
</rdf:Description>
</dcterms:subject>
<dcterms:subject>
<rdf:Description rdf:nodeID="N6d259d12d18c483db348bc0a0b45374a">
<rdf:value>Admirals -- Great Britain -- Biography</rdf:value>
<dcam:memberOf rdf:resource="http://purl.org/dc/terms/LCSH"/>
</rdf:Description>
</dcterms:subject>
<dcterms:publisher>Project Gutenberg</dcterms:publisher>
<dcterms:issued rdf:datatype="http://www.w3.org/2001/XMLSchema#date">2005-03-02</dcterms:issued>
<dcterms:hasFormat>
<pgterms:file rdf:about="http://www.gutenberg.org/files/15233/15233-8.txt">
<dcterms:isFormatOf rdf:resource="ebooks/15233"/>
<dcterms:modified rdf:datatype="http://www.w3.org/2001/XMLSchema#dateTime">2013-03-16T14:52:48</dcterms:modified>
<dcterms:format>
<rdf:Description rdf:nodeID="Nd5c53a6431ee4a81a124a068af6cc9cc">
<dcam:memberOf rdf:resource="http://purl.org/dc/terms/IMT"/>
<rdf:value rdf:datatype="http://purl.org/dc/terms/IMT">text/plain; charset=iso-8859-1</rdf:value>
</rdf:Description>
</dcterms:format>
<dcterms:extent rdf:datatype="http://www.w3.org/2001/XMLSchema#integer">115988</dcterms:extent>
</pgterms:file>
</dcterms:hasFormat>
<dcterms:rights>Public domain in the USA.</dcterms:rights>
<dcterms:creator>
<pgterms:agent rdf:about="2009/agents/5934">
<pgterms:name>Beatty, William</pgterms:name>
<pgterms:deathdate rdf:datatype="http://www.w3.org/2001/XMLSchema#integer">1842</pgterms:deathdate>
<pgterms:birthdate rdf:datatype="http://www.w3.org/2001/XMLSchema#integer">1773</pgterms:birthdate>
<pgterms:webpage rdf:resource="http://en.wikipedia.org/wiki/William_Beatty_(surgeon)"/>
</pgterms:agent>
</dcterms:creator>
<pgterms:bookshelf>
<rdf:Description rdf:nodeID="N8d8ab517be5d4d24a574a79c302445fc">
<dcam:memberOf rdf:resource="2009/pgterms/Bookshelf"/>
<rdf:value>Napoleonic(Bookshelf)</rdf:value>
</rdf:Description>
</pgterms:bookshelf>
<dcterms:hasFormat>
<pgterms:file rdf:about="http://www.gutenberg.org/files/15233/15233.zip">
<dcterms:format>
<rdf:Description rdf:nodeID="N0e16578584f8435998fb74335e273497">
<dcam:memberOf rdf:resource="http://purl.org/dc/terms/IMT"/>
<rdf:value rdf:datatype="http://purl.org/dc/terms/IMT">text/plain; charset=us-ascii</rdf:value>
</rdf:Description>
</dcterms:format>
<dcterms:modified rdf:datatype="http://www.w3.org/2001/XMLSchema#dateTime">2013-03-16T14:55:02</dcterms:modified>
<dcterms:extent rdf:datatype="http://www.w3.org/2001/XMLSchema#integer">42991</dcterms:extent>
<dcterms:isFormatOf rdf:resource="ebooks/15233"/>
<dcterms:format>
<rdf:Description rdf:nodeID="Nef4e065fb0b14e2e9d2f7ff919015e27">
<dcam:memberOf rdf:resource="http://purl.org/dc/terms/IMT"/>
<rdf:value rdf:datatype="http://purl.org/dc/terms/IMT">application/zip</rdf:value>
</rdf:Description>
</dcterms:format>
</pgterms:file>
</dcterms:hasFormat>
<dcterms:hasFormat>
<pgterms:file rdf:about="http://www.gutenberg.org/ebooks/15233.txt.utf-8">
<dcterms:isFormatOf rdf:resource="ebooks/15233"/>
<dcterms:extent rdf:datatype="http://www.w3.org/2001/XMLSchema#integer">115955</dcterms:extent>
<dcterms:format>
<rdf:Description rdf:nodeID="N00d1a7671ac647abad35d2ee8cdc7b6c">
<rdf:value rdf:datatype="http://purl.org/dc/terms/IMT">text/plain</rdf:value>
<dcam:memberOf rdf:resource="http://purl.org/dc/terms/IMT"/>
</rdf:Description>
</dcterms:format>
<dcterms:modified rdf:datatype="http://www.w3.org/2001/XMLSchema#dateTime">2017-03-08T03:35:35.071213</dcterms:modified>
</pgterms:file>
</dcterms:hasFormat>
<dcterms:hasFormat>
<pgterms:file rdf:about="http://www.gutenberg.org/files/15233/15233-h.zip">
<dcterms:extent rdf:datatype="http://www.w3.org/2001/XMLSchema#integer">414933</dcterms:extent>
<dcterms:isFormatOf rdf:resource="ebooks/15233"/>
<dcterms:format>
<rdf:Description rdf:nodeID="N639c8cfe3790493fbd031ccb3cef1290">
<dcam:memberOf rdf:resource="http://purl.org/dc/terms/IMT"/>
<rdf:value rdf:datatype="http://purl.org/dc/terms/IMT">text/html; charset=iso-8859-1</rdf:value>
</rdf:Description>
</dcterms:format>
<dcterms:modified rdf:datatype="http://www.w3.org/2001/XMLSchema#dateTime">2013-03-16T14:54:03</dcterms:modified>
<dcterms:format>
<rdf:Description rdf:nodeID="N3d06273dd12f4c14b4b2c406185c19f2">
<dcam:memberOf rdf:resource="http://purl.org/dc/terms/IMT"/>
<rdf:value rdf:datatype="http://purl.org/dc/terms/IMT">application/zip</rdf:value>
</rdf:Description>
</dcterms:format>
</pgterms:file>
</dcterms:hasFormat>
<pgterms:downloads rdf:datatype="http://www.w3.org/2001/XMLSchema#integer">24</pgterms:downloads>
<dcterms:title>Authentic Narrative of the Death of Lord Nelson</dcterms:title>
<dcterms:hasFormat>
<pgterms:file rdf:about="http://www.gutenberg.org/files/15233/15233-h/15233-h.htm">
<dcterms:modified rdf:datatype="http://www.w3.org/2001/XMLSchema#dateTime">2013-03-16T14:52:30</dcterms:modified>
<dcterms:isFormatOf rdf:resource="ebooks/15233"/>
<dcterms:format>
<rdf:Description rdf:nodeID="N1640a362e5804551a11f14ad2afcbba6">
<dcam:memberOf rdf:resource="http://purl.org/dc/terms/IMT"/>
<rdf:value rdf:datatype="http://purl.org/dc/terms/IMT">text/html; charset=iso-8859-1</rdf:value>
</rdf:Description>
</dcterms:format>
<dcterms:extent rdf:datatype="http://www.w3.org/2001/XMLSchema#integer">133225</dcterms:extent>
</pgterms:file>
</dcterms:hasFormat>
</pgterms:ebook>
<cc:Work rdf:about="">
<cc:license rdf:resource="https://creativecommons.org/publicdomain/zero/1.0/"/>
<rdfs:comment>Archives containing the RDF files for *all* our books can be downloaded at
http://www.gutenberg.org/wiki/Gutenberg:Feeds#The_Complete_Project_Gutenberg_Catalog</rdfs:comment>
</cc:Work>
<rdf:Description rdf:about="http://en.wikipedia.org/wiki/William_Beatty_(surgeon)">
<dcterms:description>Wikipedia</dcterms:description>
</rdf:Description>
</rdf:RDF>
以下是解析的内容：
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Triple (UNode "http://www.gutenberg.org/ebooks/15233.kindle.images") (UNode "dcterms:extent") (LNode (TypedL "983557" "http://www.w3.org/2001/XMLSchema#integer"))
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Triple (UNode "http://www.gutenberg.org/files/15233/15233.txt") (UNode "rdf:type") (UNode "pgterms:file")
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