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query RDF dataset

From: Jitao Yang <jitao.yang@gmail.com>
Date: Tue, 2 Jun 2009 09:51:00 +0200
Message-ID: <eb1226bd0906020051k60436073p1b5761b2c50ec0cd@mail.gmail.com>
To: semantic-web@w3.org, www-rdf-interest@w3.org
Dear all,

if I have an RDF file like:

<?xml version="1.0" encoding="utf-8"?>
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
         xmlns:dc="http://purl.org/dc/elements/1.1/"
     xmlns:vcard="http://www.w3.org/2001/vcard-rdf/3.0#">

    <rdf:Description rdf:about="http://example.org/BookJava">
        <vcard:fullname>Book Java</vcard:fullname>
        <dc:author>
            <rdf:Description rdf:about="http://example.org/BookJava/authorA
">
                 <dc:fullname>Bob Smith</dc:fullname>
                 <dc:country>Italy</dc:country>
             </rdf:Description>
        </dc:author>
        <dc:author>
            <rdf:Description rdf:about="http://example.org/BookJava/authorB
">
                 <dc:fullname>Tom Bush</dc:fullname>
                 <dc:country>Italy</dc:country>
            </rdf:Description>
        </dc:author>
    </rdf:Description>

    <rdf:Description rdf:about="http://example.org/BookCpp">
        <vcard:fullname>Book Cpp</vcard:fullname>
        <dc:author>
            <rdf:Description rdf:about="http://example.org/BookCpp/author2">
                 <dc:fullname>Mike Luck</dc:fullname>
                 <dc:country>France</dc:country>
            </rdf:Description>
        </dc:author>
        <dc:author>
            <rdf:Description rdf:about="http://example.org/BookCpp/author1">
                 <dc:fullname>Alice Bird</dc:fullname>
                 <dc:country>Italy</dc:country>
            </rdf:Description>
        </dc:author>
        <dc:author>
            <rdf:Description rdf:about="http://example.org/BookJava/authorB
">
                 <dc:fullname>kobe Mc</dc:fullname>
                 <dc:country>Italy</dc:country>
             </rdf:Description>
        </dc:author>
    </rdf:Description>

    <rdf:Description rdf:about="http://example.org/BookC">
        <vcard:fullname>Book C</vcard:fullname>
    </rdf:Description>

</rdf:RDF>

I want to query "the books whose authors are all Italian" or "the books
which have no authors",
so I use SPARQL like:

            PREFIX dc:<http://purl.org/dc/elements/1.1/>
             PREFIX vcard:<http://www.w3.org/2001/vcard-rdf/3.0#>
            SELECT DISTINCT ?bookName
            WHERE {
                    ?bookURI vcard:fullname ?bookName .
                    OPTIONAL{
                            ?bookURI dc:author ?author .
                            ?author dc:country ?country .
                            FILTER(?country = \"Italy\") .
                            OPTIONAL{
                                    ?bookURI dc:author ?author2 .
                                    ?author2 dc:country ?country2 .
                                    FILTER(?country2 != \"Italy\")
                                    }
                            FILTER(bound(?country2))
                            }
                    FILTER(!bound(?author))
                  }

I can get the right answers:
---------------
| bookName    |
===============
| "Book C"    |
| "Book Java" |
---------------
but, my original idea is FILTER(!bound(?country2)) which means filter the
books which have non-Italian authors,
however if I use  FILTER(!bound(?country2)), it will return the opposite
answers:
--------------
| bookName   |
==============
| "Book C"   |
| "Book Cpp" |
--------------
I can not understand the reasons?

Thank you very much for your help to explain to me.

Best wishes,
Jitao
Received on Tuesday, 2 June 2009 07:52:06 GMT

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