jena sparql 过滤器不提供任何输出

Question

我有一个 rdf 文件，我想查看数量少于 30.But 它不产生任何输出的书籍。

这是 rdf 文件：

<?xml version="1.0" encoding="UTF-8"?>

<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:booktique ="http://www.w3.org/2001/booktique-rdf/3.0#">

    <rdf:Description rdf:about="http://booktique.com/books/124">
        <rdf:type rdf:resource="http://booktique.com/Resource/Book"/>
        <booktique:bookID>124</booktique:bookID>
        <booktique:title>Geography</booktique:title>
        <booktique:price>10$</booktique:price>
        <booktique:author rdf:resource="http://booktique.com/authors/12999"/>
        <booktique:publisher rdf:resource="http://booktique.com/publishers/Mcgill"/>
    </rdf:Description>

    <rdf:Description rdf:about="http://booktique.com/books/258">
        <rdf:type rdf:resource="http://booktique.com/Resource/Book"/>
        <booktique:bookID>258</booktique:bookID>
        <booktique:title>Physics</booktique:title>
        <booktique:price>20$</booktique:price>
        <booktique:author rdf:resource="http://booktique.com/authors/12999"/>
        <booktique:publisher rdf:resource="http://booktique.com/publishers/Swan"/>
    </rdf:Description>`

    <rdf:Description rdf:about="http://booktique.com/books/356">
        <rdf:type rdf:resource="http://booktique.com/Resource/Book"/>
        <booktique:bookID>356</booktique:bookID>
        <booktique:title>Phyton</booktique:title>
        <booktique:price>25$</booktique:price>
        <booktique:author rdf:resource="http://booktique.com/authors/13274"/>
        <booktique:publisher rdf:resource="http://booktique.com/publishers/Connoly"/>
    </rdf:Description>



    <rdf:Description rdf:about="http://booktique.com/authors/12999">
        <rdf:type rdf:resource="http://booktique.com/Resource/Author"/>
        <booktique:name>James Brown</booktique:name>
        <booktique:authorID>12999</booktique:authorID>
        <booktique:e-mail>brown@gmail.com</booktique:e-mail>
    </rdf:Description>

    <rdf:Description rdf:about="http://booktique.com/authors/13274">
        <rdf:type rdf:resource="http://booktique.com/Resource/Author"/>
        <booktique:name>Kelly Smith</booktique:name>
        <booktique:authorID>13274</booktique:authorID>
        <booktique:e-mail>smith@gmail.com</booktique:e-mail>
    </rdf:Description>

    <rdf:Description rdf:about="http://booktique.com/publishers/Connoly">
        <rdf:type rdf:resource="http://booktique.com/Resource/Publisher"/>
        <booktique:name>Connoly</booktique:name>
        <booktique:address>US</booktique:address>
    </rdf:Description>

    <rdf:Description rdf:about="http://booktique.com/publishers/Mcgill">
        <rdf:type rdf:resource="http://booktique.com/Resource/Publisher"/>
        <booktique:name>Mcgill</booktique:name>
        <booktique:address>UK</booktique:address>
    </rdf:Description>

    <rdf:Description rdf:about="http://booktique.com/publishers/Swan">
        <rdf:type rdf:resource="http://booktique.com/Resource/Publisher"/>
        <booktique:name>Swan</booktique:name>
        <booktique:address>FRA</booktique:address>
    </rdf:Description>

    <rdf:Description rdf:about="http://booktique.com/sales/book/124">
        <rdf:type rdf:resource="http://booktique.com/Resource/SalesOrder"/>
        <booktique:bookID rdf:resource="http://booktique.com/books/124"/>
        <booktique:amount>100</booktique:amount>

    </rdf:Description>

    <rdf:Description rdf:about="http://booktique.com/sales/book/258">
        <rdf:type rdf:resource="http://booktique.com/Resource/SalesOrder"/>
        <booktique:bookID rdf:resource="http://booktique.com/books/258"/>
        <booktique:amount>12</booktique:amount>

    </rdf:Description>

    <rdf:Description rdf:about="http://booktique.com/sales/book/356">
        <rdf:type rdf:resource="http://booktique.com/Resource/SalesOrder"/>
        <booktique:bookID rdf:resource="http://booktique.com/books/356"/>
        <booktique:amount>20</booktique:amount>

    </rdf:Description>

JENA 代码：

static void sparqltest()

{

FileManager.get().addLocatorClassLoader(Test.class.getClassLoader());
Model model= FileManager.get().loadModel("booktique.rdf");
String queryString="PREFIX rdf:<http://www.w3.org/2001/booktique-rdf/3.0#>"+ 
"SELECT * WHERE {?s rdf:amount ?x."+
                    "FILTER (?x<30)}";
Query query= QueryFactory.create(queryString);
QueryExecution qexec=QueryExecutionFactory.create(query, model);

try { ResultSet results = qexec.execSelect();while ( results.hasNext()){ QuerySolution soln = results.nextSolution(); Literal amount = soln.getLiteral("x"); System.out.println(amount); } }

我查了apache网站和很多网站，怎么解决都解决不了 problem.I 有2个资源少于30.So 我怎么解决这个问题？谢谢。

Answer 1

<booktique:amount>12</booktique:amount> 是一个包含字符“1”和“2”的字符串值。这不是一个数字。

您需要：

在数据中，为属性值指定数据类型。
在您的查询中将其转换为整数 xsd:integrer(?x) < 30。

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